JS基础测试37期

[zhangxinxu]

本期小测关于字符格式处理：

答题前不要看别人回答，答题后可以，但不能修改自己回答

大家提交回答的时候，注意缩进距离，起始位置从左边缘开始；另外，github自带代码高亮，所以请使用下面示意的格式。

```js
// 你的JS代码写在这里
 ```

其它：

1. 首位答题者可获得直播翻牌机会；
2. 本次答疑直播为9月7日上午10:00，大约30分钟；

[theDrunkFish]

题目1

//zxx: 如果原本格式就有空格会有问题
var bankCode = '6222081812002934027';
console.log(bankCode.replace(/(\d{4})/g, '$1 '));

题目2

• 方法1

  var numberCode = '5702375';
  console.log(Number(numberCode).toLocaleString());

• 方法2

  // zxx: 此方法小数无效
  var numberCode = '5702375';
  console.log(numberCode.replace(/(\d)(?=(\d{3})+$)/g, '$1,'));

题目3

 var filesize = 2837475;

function formatterFilesize(size, n){
    var K = 1024;
    var M = 1024 ** 2;
    var G = 1024 ** 3;

    if(size < M){
        return roundNumber(size / K, n) + 'K';
    }else if(size < G){
        return roundNumber(size / M, n) + 'M';
    }else{
        return roundNumber(size / G, n) + 'G';
    }
}
function roundNumber(number, n=2){
    return Math.round(number * Math.pow(10, n)) / (Math.pow(10, n));
}
console.log(formatterFilesize(filesize))
console.log(formatterFilesize(475)); // size < 1K
console.log(formatterFilesize(4475)); // size < 1M
console.log(formatterFilesize(5548475)); // 1M <= size < 1G
console.log(formatterFilesize(6568358465)); // 1G <= size

[juzhiqiang]

// 1.  js 处理
// zxx: 你这个方法我没跑起来，a改成arr结果也不对
    var bankCode = "6222081812002934027";
    var arr = [4,4,4,4,3];
    var newCode = "";
    arr.forEach(item => {
       //a指的是bankCode
    newCode += item == arr[arr.length-1] ?  a.slice(0,item) : a.slice(0,item)+" "; 
    })
   bankCode  = newCode 
 //正则处理
   var bankCode = "6222081812002934027";
   bankCode = bankCode.replace(/(\d{4})/g, '$1 ')

2. 
   // zxx: 小数无效
   function moneySlice(money){
       //格式不正确抛出异常
   if(isNaN(money)) return Error('请传入纯数字');
   let moneys = money ? money.toString() : money;
   return moneys.replace(/(\d)(?=(\d{3})+$)/g, '$1,');
   }

3. 首先说下获取回来的文件大小单位都是比特 且 1024B = 1K 1024K = 1M 1024M = 1G; 测试用例 var test = [100,1050,2837475,28374756565];

function unit(num){ var K = 1024, M = 1024 1024 , G = 1024 1024 * 1024; if(num > G) return (num / G ).toFixed(2) + 'G' ; if(num > M) return (num / M).toFixed(2) + 'M'; return (num / K).toFixed(2) + 'K' ; } console.log(unit(filesize)); 执行测试用例打印 test.forEach(=>{ console.log(unit()); })

[les-lee]

    var card_num = '6222081812002934027'
    var result1 = card_num.replace(/(\d{4})/g, '$1 ')
    console.log(result1)

    //zxx: 小数有问题
    var numberCode = '5702375'
    var result2 = numberCode.replace(/(?!^)(?=(\d{3})+$)/g, ',')
    console.log(result2)

    // zxx: 最好取几位小数，最好单位大写 
    var filesize = 2837475

    function normalizeFilesize(filesize) {
      if (typeof filesize != 'number' || filesize < 0) {
        throw Error('参数不合法')
      }
      var gvalue = filesize / 1024 / 1024 / 1024
      if (gvalue > 1) {
        return gvalue + 'g'
      }
      var mvalue = gvalue * 1024
      if (mvalue > 1) {
        return mvalue + 'm'
      } else {
        return (mvalue * 1024) + 'k'
      }
    }

    console.log(normalizeFilesize(filesize))

[fzero17]

1.

//zxx: 题目不是这个意思
var bankCode = '6222081812002934027';
var result = bankCode.split('').join(' ');
console.log(result);

2.

// zxx: 没必要取整
var numberCode = '5702375';
var result = parseInt(numberCode).toLocaleString();
console.log(result);

3.

//zxx: 只取一位小数有点少
var filesize = 2837475;
function convertFileSize(fileSizeInBytes) {
    var i = -1;
    var byteUnits = [' KB', ' MB', ' GB'];
    do {
        fileSizeInBytes = fileSizeInBytes / 1024;
        i++;
    } while (fileSizeInBytes > 1024 && i < 2);

    return Math.max(fileSizeInBytes, 0.1).toFixed(1) + byteUnits[i];
};

var result = convertFileSize(filesize);
console.log(result);

[liyongleihf2006]

//第一题
// zxx: 棒棒哒，还差一点
var bankCode = "6222081812002934027";
console.log(bankCode.replace(/(?!^)(?=(\d{4})*\d{3}$)/g,"$& "))
//第二题
//zxx: 小数的问题
var numberCode = "5702375";
console.log(numberCode.replace(/(?!^)(?=(\d{3})+$)/g,"$&,"));
//第三题
//zxx: 最好取个几位小数
var filesize = 2837475;
console.log(formatter(filesize));
function formatter(filesize){
      var K = 1024,
          M = 1024 **2 ,
          G =  1024 **3;
    if(filesize > G) return (filesize / G ) + 'G' ;
    if(filesize > M) return (filesize / M)  + 'M';
    return (filesize / K)  + 'K' ;
}

[NeilChen4698]

1.

// zxx: 如果原本有空格，这个方法很危险
var convertBankCode = function(val) {
    return (val === null || val === undefined ? '' : (val + '')).substring(0,19).replace(/(.{4})/g,'$1 ');
};
console.log(convertBankCode('6222081812002934027'));

2.

var convertNumber = function(val) {
    val = +(val === null || val === undefined ? '' : (val + ''));
    return isNaN(val) ? NaN : val.toLocaleString();
};
console.log(convertNumber('5702375'));
console.log(convertNumber('57023.75'));
console.log(convertNumber('570a75'));

3.

var convertFileSize = function(val) {
    if (val === null) {
        return val;
    } else if (isNaN(val)) {
        return NaN;
    } else {
        var kbSize = 1024;
        var mbSize = 1024 * 1024;
        var gbSize = 1024 * 1024 * 1024;
        if (val < mbSize) {
            return Math.round(val * 100 / kbSize) / 100 + 'K';
        } else if (val < gbSize) {
            return Math.round(val * 100 / mbSize) / 100 + 'M';
        } else {
            return Math.round(val * 100 / gbSize) / 100 + 'G';
        }
    }
};
console.log(convertFileSize(1000));
console.log(convertFileSize(1030));
console.log(convertFileSize(1024 * 1040));
console.log(convertFileSize(1024 * 1024 * 1050));

[mx52jing]

第一题

//zxx: 原本有空格就凉凉了
var bankCode = "6222081812002934027";

var result = bankCode.split('').reduce((a, b) => {
  return a.replace(/\s/g, '').length % 4 === 0 ? `${a} ${b}` : `${a}${b}`
})
console.log(result)

第二题

//zxx: 这个正则可以的，支持小数
var numberCode = "5702375",
      reg = /\B(?=(\d{3})+(?!\d))/g
console.log(numberCode.replace(reg, ','))

第三题

// zxx: 最好取几位小数
var size = 2837475

function foo(size){
  var K = 1024,
      M = K * 1024,
      G = M * 1024,
      _K = size/K,
      _M = size/M,
      _G = size/G
  if(_G>1) return `${_G}G`
  if(_M>1) return `${_M}M`
  return `${_K}K`
}

console.log(foo(size))

[nichoasurey]

张大大这是暗示往 6222 0818 1200 2934 027 里打 5,702,375 吗？

// zxx: 代码高亮有问题，题1题2均有问题
function formatStr(soure,format,insertStr,loopFormat=false,forward=true,needEnd=false,protect=1000) {
    var resultStr = '';
    if(forward){
      for(var i=0,j=0;i<format.length && j<soure.length;protect--){
        if(protect<0){
          console.log('over limit times');
          console.log('limit times: ',protect);
          break;
        }
        resultStr+=soure.slice(j,j+format[i])+insertStr;
        j+=format[i];
        i++;
        if(loopFormat && i>=format.length){
          i=0
        }
      }
      if(!needEnd){
        resultStr = resultStr.substring(0,resultStr.length-insertStr.length)
      }
    }
    else{
      for(var i=0,j=soure.length;i<format.length && j>0;protect--){
        if(protect<0){
          console.log('over limit times');
          console.log('limit times: ',protect);
          break;
        }
        var start = j-format[i];
        if(start<0){
          start = 0;
        }
        resultStr=insertStr+soure.slice(start,j)+resultStr;
        j=start;
        i++;
        if(loopFormat && i>=format.length){
          i=0
        }
      }
      if(!needEnd){
        resultStr = resultStr.substring(insertStr.length)
      }
    }
    return resultStr
  }
第一题：
var bankCode = '6222081812002934027';
formatStr(bankCode,[4,4,4,4,3],' ')
第二题：
var numberCode = '5702375';
formatStr(numberCode,[3],',',true,false);
第三题：
var fileSize = 2837475;
  function showFileSize(fileSize) {
    var K = 1024,M = 1048576,G = 1073741824;
    if(fileSize > G){
      return (fileSize/G).toFixed(3)+'G';
    }
    else if(fileSize > M){
      return (fileSize/M).toFixed(3)+'M';
    }
    else if(fileSize > K){
      return (fileSize/K).toFixed(3)+'K';
    }
    else {
      return fileSize+'B';
    }
  }
showFileSize(fileSize);

https://www.zhangxinxu.com/wordpress/2017/09/web-page-comma-number/

[Seasonley]

//第一题
var bankCode = '6222081812002934027';
bankCode.replace(/\S{4}/g,v=>v+' ');
//"6222 0818 1200 2934 027" bankCode = '6222081812002934027';
//"6222 0818 1200 293X XXX" bankCode = '622208181200293XXXX';

//第二题
var numberCode = '5702375';
(+numberCode).toLocaleString('en-US',{useGrouping:true});
//"5,702,375"  numberCode = '5702375';
//"845"        numberCode = '845';
//"34,384.523" numberCode = '34384.5234';
//了解更多js国际化 https://segmentfault.com/a/1190000018685063

//第三题
//  zxx: filesize是字节大小哟~
var filesize = 2837475;
(filesize>>20?filesize/2**20+'G'
 :filesize>>10?filesize/2**10+'M'
 :filesize+'K')
.replace(/(?<=\.)\d+/,v=>Math.round(v/10**(`${v}`.length-2)))
//"2.71G" filesize = 2837475;
//"2.77M" filesize = 2837;
//"283K"  filesize = 283;

//补一个函数式的
Array.from({length:3},v=>filesize)
.map((v,i)=>[(v/2**(i*10)).toFixed(2),'KMG'[i]])
.find((v,i)=>v[0]<1024||i==2).join('')
//"2.71G" filesize = 2837475;

[frankyeyq]

1. bankCode.replace(/(\d{4})/g, '$1 ')
2. Number(numberCode).toLocaleString()
3.
function formatFileSize(fileSize) {
    const K = 1024;
    const M = K * 1024;
    const G = M * 1024
    if (fileSize < M) {
        return (fileSize / K).toFixed(2) + 'K'
    } else if (fileSize > M) {
        return (fileSize / M).toFixed(2) + 'M'
    } else if (fileSize > G) {
        return (fileSize / G).toFixed(2) + 'G'
    }
}
var newSize = formatFileSize(filesize);

[JaimeCheng]

测试demo

// 第 1 题
var bankCode = '6222081812002934027';
console.log(bankCode.trim().replace(/(\d{4})(?=\d)/g, "$1 "));

// 第 2 题
var numberCode = '5702375';
console.log(Number(numberCode).toLocaleString()) // 两种都可
console.log(Number(numberCode).toLocaleString('en-US'))

// 第 3 题
var filesize = 2837475;
var res = formatSize(filesize)

function formatSize (size = Number(size)) {
  if (isNaN(size)) {
    return '请使用合法数值'
  }
  const unit = 1024
  var res = ''
  switch (true) {
    case size < Math.pow(unit, 2): 
      res = (size / unit).toFixed(2) + "K"
      break
    case size < Math.pow(unit, 3):
      res = (size / Math.pow(unit, 2)).toFixed(2) + "M";
      break
    case size < Math.pow(unit, 4):
      res = (size / Math.pow(unit, 3)).toFixed(2) + "G";
  }
  return res
}

[lisachen]

1.

bankCode.replace(/(\d{4})(?=(\d)+$)/g,'$1 ');

2.

Number(numberCode).toLocaleString()

numberCode.replace(/(\d)(?=(\d{3})+$)/g,'$1,');

3.

function filesSizeFormat(size) {
  let k = size / 1024,
    m = k / 1024,
    g = m / 1024;
  return g >= 1 ? g + 'G' : m >= 1 ? m + 'M' : k + 'K';
}

[guqianfeng]

    let bankCode = '6222081812002934027';
    bankCode = bankCode.replace(/(\d{4})/g, "$1 ");
    console.log(bankCode);

    let numberCode = '5702375';
    numberCode = numberCode.replace(/(?!^)(?=(\d{3})+$)/g, ",")
    console.log(numberCode);

    let filesize = 2837475;
    const getSize = (size) => {
        let k = (size / 1024).toFixed(2);
        let m = (size / 1024).toFixed(2);
        let g = (m / 1024).toFixed(2);
        return g >= 1 ? g + "G" : m >= 1 ? m + "M" : k + "K";
    };
    console.log(getSize(filesize));

    function replaceRule(reg){
        return function(str, replaceContent){
            console.log(str.replace(reg, replaceContent));
            return str.replace(reg, replaceContent);
        }
    };

    console.log("------------------------测试用例银行卡号---------------------------------")
    let bankRule = replaceRule(/(\d{4})/g);
    bankRule("6222081812002934027", "$1 ")
    bankRule("1".repeat(19), "$1 ")
    bankRule("2".repeat(19), "$1 ")

    console.log("------------------------测试用例钱---------------------------------")
    let moneyRule = replaceRule(/(?!^)(?=(\d{3})+$)/g);
    moneyRule("5702375", ",")
    moneyRule("10", ",")
    moneyRule("2000", ",")
    moneyRule("123456789", ",")
    moneyRule("11111111111111111111111111111111", ",")

    console.log("------------------------测试用例文件大小---------------------------------")
    console.log(getSize(2837475));
    console.log(getSize(2090));
    console.log(getSize(1024 ** 2 + 6666));
    console.log(getSize(5201314));

[sghweb]

测试demo

<div>
  <input type="number" id="cardinput"><button id="card">卡号</button><span class="cardtxt"></span>
</div>
<div>
  <input type="number" id="moneyinput"><button id="money">人民币</button><span class="moneytxt"></span>
</div>
<div>
  <input type="number" id="fileinput"><button id="file">文件大小</button><span class="filetxt"></span>
</div>

// 第一题
// zxx: 和题意不符
function bankformat(card) {
  return card.replace(/(.{1})/g, "$1 ")
}
// 第二题
function format(num) {
  var reg = /\d{1,3}(?=(\d{3})+$)/g;
  return (num + '').replace(reg, '$&,');
}
// 第三题
function getfilesize(size) {
  if (!size)
    return "";
  var num = 1024.00; //byteCCC
  if (size > Math.pow(num, 3)) {
    return (size / Math.pow(num, 3)).toFixed(2) + "G"; //G
  } else if (size > Math.pow(num, 2)) {
    return (size / Math.pow(num, 2)).toFixed(2) + "M"; //M
  } else {
    return (size / num).toFixed(2) + "K"; //kb
  }
}
// 测试
let card = document.querySelector("#card")
let money = document.querySelector("#money")
let file = document.querySelector("#file")
let cardtxt = document.querySelector(".cardtxt")
let moneytxt = document.querySelector(".moneytxt")
let filetxt = document.querySelector(".filetxt")
card.addEventListener("click", function() {
  let val = document.querySelector("#cardinput").value
  cardtxt.innerHTML = bankformat(val)
})
money.addEventListener("click", function() {
  let val = document.querySelector("#moneyinput").value
  moneytxt.innerHTML = format(val)
})
file.addEventListener("click", function() {
  let val = document.querySelector("#fileinput").value
  filetxt.innerHTML = getfilesize(val)
})

[zengqingxiao]

测试 第一题

    var bankCode = '1234123412341234123'
    function one(bankCode) {
      var oneReg = /(\d{4})/g
      var newOneStr = bankCode.replace(oneReg, function (word) {
        word = word + ' '
        return word
      })
      console.log('第一题答案:', newOneStr)
    }
    one(bankCode) // 第一题答案: 1234 1234 1234 1234 123

第二题 方法一

    var numberCode = 5702375.222
    function two1(numberCode) {
      var newTwoStr = parseFloat(numberCode).toLocaleString()
      console.log('第二题的答案:', newTwoStr) // 5,702,375.222
    }
    two1(numberCode) // 第二题的答案: 5,702,375.222

方法二

    var numberCode = 5702375.222
    function two2(num) {
      var numberCode = num.toString()
      var twoReg1 = /^\d+/g
      var twoReg2 = /(?=(\B)(\d{3})+$)/g
      var newTwoStr = numberCode.replace(twoReg1, function (word) {
        // console.log(word)
        word = word.replace(twoReg2, function (word2) {
          // console.log(word2)
          word2 = ',' + word2
          return word2
        })
        // console.log(word)
        return word
      })
      console.log('第二题的答案:', newTwoStr) // 第二题的答案: 5,702,375.222
    }
    two2(numberCode)

第三问

    var filesize = 2837475
    function three(filesize) {
      if (parseInt(filesize) < 1024 || parseInt(filesize) === 1024) {
        console.log('第三题的答案:', filesize.toFixed(3) + 'K')
      }

      if (parseInt(filesize) > 1024 && parseInt(filesize) < 1024 * 1024) {
        console.log('第三题的答案:', (filesize / 1024).toFixed(3) + 'M')
      }
      if (parseInt(filesize) > 1024 * 1024 || parseInt(filesize) === 1024 * 1024) {
        console.log('第三题的答案:', (filesize / (1024 * 1024)).toFixed(3) + 'G')
      }
    }
    three(filesize) // 第三题的答案: 2.706G

[asyncguo]

// 第一题
let test1 = '6222081812002934027'.replace(/(\d{4})(?=(\d))/g, '$1 ')
console.log(test1)
// 保证最后一位始终不会出现空格
let test2 = '62220818120029340270'.replace(/(\d{4})(?=(\d))/g, '$1 ')
console.log(test2)

// 第二题
let test3 = '5702375'.replace(/(?!^)(?=(\d{3})+$)/g, ',')
console.log(test3)
// 保证第一位始终不会出现分隔符
let test4 = '570237'.replace(/(?!^)(?=(\d{3})+$)/g, ',')
console.log(test4)

// 第三题
function formatSize(size) {
  size = parseFloat(size) / 1024
  let unitArr = ['K', 'M', 'G']
  let _index = 0
  while(size / 1024 >= 1 && _index < unitArr.length - 1) {
    size = size / 1024
    ++_index
  }
  return `${size}${unitArr[_index]}`
}
console.log(formatSize(2837475))
console.log(formatSize(12))
console.log(formatSize(1024))
console.log(formatSize(1024*1000))
console.log(formatSize(1024*1024))
console.log(formatSize(1024*1024*1000))
console.log(formatSize(1024*1024*1024))
console.log(formatSize(1024*1024*1024*1000))
console.log(formatSize(1024*1024*1024*1024))

[zy017]

// 1
var bankCode = '6222081812002934027'

// 方法一
var transBankCode = function(code) {
    var len = parseInt(code.length / 4)
    var str = ''
    for (var i = 1; i <= len; i++) {
        str += `${code.slice(4 * (i - 1), 4 * i)} `
    }
    str += code.slice(4 * len, 4 * (len + 1))
    return str
}
console.log(transBankCode(bankCode))

// 方法二 使用正则表达式
console.log(bankCode.replace(/\S{4}/g, i => i + ' '))

// 2
var numberCode = '5702375'
// 方法一
var transNumberCode = function(code) {
    var len = parseInt(code.length / 3)
    var str = ''
    for (var i = 1; i <= len; i++) {
        var a = -3 * i
        var b = -3 * (i - 1)
        if (b === 0) {
            str = `,${code.slice(a)}` + str
        } else {
            str = `,${code.slice(a, b)}` + str
        }
    }
    str = code.slice(0, -(3 * len)) + str
    return str
}
console.log(transNumberCode(numberCode))
// 方法二 正则表达式
console.log(numberCode.replace(/(?<=\d)(?=(\d{3})+\b)/g, i => ',' + i))

// 方法三 
console.log(Number(numberCode).toLocaleString())

// 3
// 转换文件大小 
var filesize = 2837475
// n 是传入文件的大小 p是保留几位小数(默认取两位小数)
var transFileSize = function(n, p = 2) {
    function round(number, precision) {
        return Math.round(+number + 'e' + precision) / 10 ** precision;
    }
    n = Number(n)
    if (isNaN(n)) {
        return 0
    }
    if (n < 1024 ** 2) {
        return `${round(n / 1024, p)}K`
    } else if (n >= 1024 ** 2 && n < 1024 ** 3) {
        return `${round(n / (1024 ** 2), p)}M`
    } else {
        return `${round(n / (1024 ** 3), p)}G`
    }
}

console.log(transFileSize(filesize))

[CMYK99]

题目1

function splitBankCode (code) {
return code.replace(/(\d{4})/g, '$1 ').trim()
}
//19位银行卡号
console.log(splitBankCode('6222081812002934027'))
//16位银行卡号
console.log(splitBankCode('6222081812002934'))

题目2

function splitNumber (num) {
num = String(num);
if (num.length>3)  {
return splitNumber(num.substr(0,  num.length - 3))  +  ','  +  num.substr(-3)
} else return num
}
console.log(splitNumber(12345));
console.log(splitNumber(123456));
console.log(splitNumber(1234567));

题目3

function format (size) {
let K = 1024;
let M = 1024 * K;
let G = 1024 * M;
let units = [{
size: G,
name: 'G'
}, {
size: M,
name: 'M'
}, {
size: K,
name: 'K'
}]
for (let i=0; i<units.length; i++) {
if (units[i].size<=size || size<K) {
return (size / units[i].size).toFixed(2) + units[i].name
}
}
}
console.log(format(2837475));
console.log(format(676552834));
// zxx：你这个为什么返回undefined
// 之前判断写反了...
console.log(format(98765432111));

[fzpijl]

demo 1.

var bankCode = '6222081812002934027';
var bankReg = /(?!^)(?=(\d{4})+\d{3}$)|(?=\d{3}$)/g
bankCode = bankCode.replace(bankReg, function () {
    return ' '
})

2.

var numberCode = '5702375';
var numReg = /(?=(\d{3})+$)/g
numberCode = numberCode.replace(numReg, function () {
    return ','
})

3.

var filesize = 2837475;
function format(size) {
    var newSize;
    var kSize = 1024;
    var mSize = 1024 * 1024;
    var gSize = 1024 * 1024 * 1024;

    if(size >= gSize){
        newSize = (size / gSize).toFixed(2)  + 'G';
    }else if(size >= mSize){
        newSize = (size / mSize).toFixed(2) + 'M';
    }else {
        newSize = (size / kSize).toFixed(2) + 'K';
    }

    return newSize
}

[GitHdu]

1. 
var bankCode = '6222081812002934027';
let i=0
let arr = []
while(i<bankCode.length) {
  arr.push(bankCode[i])
  i++
  if (i%4===0) {
    arr.push(' ')
  }
}
console.log(arr.join(''))

2. 
var numberCode = '5702375';
var start = numberCode.length%3
var startStr = numberCode.slice(0,start)+','
let j = start
while(j<numberCode.length) {
  startStr+=numberCode[j]
  j++
  if((j-start)%3===0){
    startStr+=','
  }
}
let retStr = startStr.slice(0,-1)
console.log(retStr)

3. 
var filesize = 2837475;
var sizes = ['K', 'M', 'G'];
var i = parseInt(Math.floor(Math.log(filesize) / Math.log(1024)));
i = i>3?3:i
// 保留两位小数
var ret =Math.round(filesize*100 / Math.pow(1024, i))/100 + sizes[i-1];
console.log(ret)

[hangfengnice]

1.

var bankCode = '6222081812002934027';
console.log(bankCode.replace(/(\d{4})/g, '$1 '));

2.

// zxx: 不错，支持小数
var numberCode = '995702375';
console.log(numberCode.replace(/\B(?=(\d{3})+\b)/g,  ','));

3.

function formatFileSize (filesize = 1023) {
  let K = 1024,
      M = 1024 ** 2,
      G = 1024 ** 3;

  switch(true) {
    case filesize > G:
      return (filesize / G).toFixed(1) + "G";
    case filesize > M:
      return (filesize / M).toFixed(1) + "M";
    case filesize > K:
      return (filesize / K).toFixed(1) + "K";
    default:
      return filesize + "B";
  }
}
console.log(formatFileSize());
console.log(formatFileSize(1025));
console.log(formatFileSize(1024 ** 2 + 1));
console.log(formatFileSize(1024 ** 3 + 1));

[wingmeng]

第 1 题：

var backCode = '6222081812002934027';

// 方法1
var result = backCode.replace(/(\d{4})/g, '$1 ');
console.log(result);  // "6222 0818 1200 2934 027"

// 方法2
var result = backCode.split(/(\d{4})/).filter(s => !!s).join(' ');
console.log(result);  // "6222 0818 1200 2934 027"

第 2 题：

var numberCode = ‘5702375’;
var result = numberCode.replace(/\d{1,3}(?=(\d{3})+$)/g, '$&,');  // 未考虑小数情况
console.log(result);  // "5,702,375"

第 3 题：

var filesize = 2837475;

function matchUnit(value) { 
  var sizeUnits = ['K', 'M', 'G'];
  var sizeRadix = 1024;

  if (value < sizeRadix) {
    return (value / sizeRadix).toFixed(1) + sizeUnits[0]
  }

  for (var i = sizeUnits.length - 1; i >= 0; i--) {
    var radix = Math.pow(sizeRadix, i + 1);
    if (value >= radix) {
      return (value / radix).toFixed(1) + sizeUnits[i]
    }
  }
}

console.log(matchUnit(filesize));  // 2.7M
console.log(matchUnit(100));  // 0.1K
console.log(matchUnit(10000));  // 9.8K
console.log(matchUnit(100000000));  // 95.4M
console.log(matchUnit(10000000000));  // 9.3G

[XboxYan]

//1
var bankCode = '6222081812002934027';
bankCode.replace(/(\d{4})/g,'$1 ');

//2
var numberCode = '5702375';
Number(numberCode).toLocaleString('en-US');

//3
var filesize = 2837475;
function format(size){
    return size>1024**3&&(size/1024**3).toFixed(2)+'G' || 
           size>1024**2&&(size/1024**2).toFixed(2)+'M' || 
           (size/1024).toFixed(2)+'K';
}

format(2837475555) //2.64G
format(2837475) //2.71M
format(28374) //27.71K

[livetune]

第一题

var bankCode = '6222081812002934027'
var formatterCode = bankCode.replace(/(\d{4})(?!$)/g, '$1')
console.log(formatterCode)

第二题

var numberCode = 5702375
var formatterNumberCode = numberCode.toLocaleString()
console.log(formatterNumberCode)
// or
numberCode = 1024.1235888
var formatterNumberCode = String(numberCode).replace(/(?<!\.\d*)\B(?=(\d{3})+(?!\d))/g, ',')
console.log(formatterNumberCode)

第三题

//3. 
var filesize = 2837475;
function formatterFilesize(filesize) {
    if (filesize < 1024 ** 2) {
        return filesize / 1024 + 'KB'
    } else if (1024 ** 2 <= filesize && filesize < 1024 ** 3) {
        return filesize / (1024 ** 2) + 'MB'
    } else {
        return filesize / (1024 ** 3) + 'GB'
    }
}
console.log(formatterFilesize(filesize))
console.log(formatterFilesize(1024))
console.log(formatterFilesize(1024 ** 2))
console.log(formatterFilesize(1024 ** 3))

[Despair-lj]

demo

// 1
var bankCode = '6222081812002934027';
var firstResult = bankCode.replace(/(\d{4})/g, '$1 ');
console.log(firstResult);

// 2
var numberCode = '5702375';
var secondResult = (+numberCode).toLocaleString('en-US');
console.log(secondResult);
var secondAnthor = numberCode.replace(/\B(?=(\d{3})+$)/g, ',');
console.log(secondAnthor)

// 3
var UNITS = ['K', 'M', 'G'];
function bytesToSize(number) {
  if (!Number.isFinite(number)) {
    throw new Error('需求有限数值, 却得到 ' + typeof number + ':' + number);
  }
  number = number / 1000;
  var isNegative = number < 0;
  var prefix = isNegative ? '-' : '';

  if (isNegative) {
    number = -number;
  }

  if (number < 1) {
    return prefix + number + ' ' + UNITS[0];
  }

  var exponent = Math.min(
    Math.floor(Math.log10(number) / 3),
    UNITS.length - 1
  );
  number = (number / Math.pow(1000, exponent)).toPrecision(3);

  return prefix + number + ' ' + UNITS[exponent];
}

var filesize = -2837475;
var thirdResult = bytesToSize(filesize);
console.log(thirdResult);

[lifelikejuly]

Demo

第一题

var bankCode = "6222081812002934027";
bankCode = bankCode.replace(/(\d{4})(?=\d)/g, "$1 ");
console.log(bankCode);

第二题

var numberCode = '5702375';
numberCode = parseInt(numberCode).toLocaleString();
console.log(numberCode);

第三题

var fileSize = 2837475;
var K = 1024;
var M = 1024 * 1024;
var G = 1024 * 1024 * 1024;
var size = "";
if(fileSize >= G){
  size = (fileSize / G).toFixed(2)  + "G";
}else if(fileSize >= M){
   size = (fileSize / M).toFixed(2)  + "M";
}else{
   size = (fileSize / K).toFixed(2)  + "K";
}
console.log(size);

[rayj1993]

demo

// 第一题
//zxx: mark，有意思的实现
let bankCode = '6222081812002934027';

let bankCodeArr = bankCode.match(/\d{3,4}/g);
document.write(bankCodeArr.join(' '));
document.write('<br/>');

// 第二题
let numberCode = '5702375';

let numberCodeReverse = numberCode.split('').reverse().join('');
let numberCodeArr = numberCodeReverse.match(/\d{1,3}/g);
document.write(numberCodeArr.reverse().join(','));
document.write('<br/>');

// 第三题 K,M,G
let fileSize = 2837475;
let K = 1024;
let size = '';
if (fileSize >= K ** 3) {
    size = (fileSize / K ** 3).toFixed(2) + "G";
} else if (fileSize >= K ** 2) {
    size = (fileSize / K ** 2).toFixed(2) + "M";
} else {
    size = (fileSize / K).toFixed(2) + "K";
}
document.write(size);

[silverWolf818]

function formatNumber(num) {
    var result = '';
    while (num.length > 3) {
        result = ',' + num.slice(-3) + result;
        num = num.slice(0, num.length - 3);
    }
    if (num) {
        result = num + result;
    }
    return result;
}

function formatFileSize(size) {
    var K = 1024, M = K * K, G = M * K;
    if (size > G) {
        return (size / G).toFixed(2) + 'G';
    } else if (size > M) {
        return (size / M).toFixed(2) + 'M';
    } else {
        return size + 'K';
    }
}

//第一题
"621483018499184".replace(/(\d{4})(?=\d)/g, "$1 ");
//第二题
parseInt("5702375").toLocaleString();

console.log(parseInt("5702375").toLocaleString());
//Intl.NumberFormat是对语言敏感的格式化数字类的构造器类
//具体语法参考https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/NumberFormat
console.log(new Intl.NumberFormat().format(parseInt("5702375")));
console.log(formatNumber("5702375"));
//第三题
console.log(formatFileSize(2837475));
console.log(formatFileSize(234));
console.log(formatFileSize(5367367369));

[GCGligoudan]

// 1
var bankCode = '6222081812002934027';
var formatCode = `${bankCode.slice(0,4)} ${bankCode.slice(4,8)} ${bankCode.slice(8,12)} ${bankCode.slice(12,16)} ${bankCode.slice(16)}`;

// 2
// 简单的
var numberCode = '5702375';
var formatNumber = Number.prototype.toLocaleString.apply(parseInt(numberCode, 10));

// 从数字后面循环
var numberCode = '5702375';
var formatNumber1 = '';
while(numberCode.length>3){
  formatNumber1 = ','+numberCode.slice(-3)+formatNumber1;
  numberCode = numberCode.slice(0, -3);
}
if (numberCode) formatNumber1 = numberCode+formatNumber1;

// 使用正则，从后面向前匹配
var numberCode = '5702375';
var formatNumber2 = numberCode.replace(/(\d)(?=(?:\d{3})+$)/g, '$1,');

// 3 1GB = 1024MB = 1024*1024KB = 1024*1024*1024B
var filesize = 2837475;

function transMemory(volume, current){
  if(!current) current = '';
  if (volume < 1024 * 1024) { // 如果容量小于1mb
    return current + volume / 1024 + 'K';
  } else if( volume < 1024 * 1024 * 1024 ) { // 如果容量小于 1GB
    return transMemory(volume % (1024 * 1024), current+Math.floor(volume / (1024 * 1024))+'M');
  } else { // 容量大于1GB
    return transMemory(volume % (1024 * 1024 * 1024), current+Math.floor(volume / (1024 * 1024 * 1024))+'G');
  }
}
var formatSize = transMemory(filesize);
// formatSize输出结果为：2M722.9716796875K

console.log(transMemory(123456789)); // 117M755.2705078125K
console.log(transMemory(74125896365)); // 69G35M986.6689453125K
// 容量在线转换工具结果在下面，有图片

[ghost]

1

var bankcode = '6222081812002934027'
let func1 = (code) => {
  let length = code.length
  if (length === 19) {
    let arr = []
    for (let i = 0; i < length; i += 4) {
      arr.push(code.slice(i, i + 4))
    }
    let result = arr.join(' ')
    return result
  } else {
    return 'not valid bankcode'
  }
}
// test
console.log(func1(''))
console.log(func1(bankcode))
console.log(func1(bankcode + '1'))

2

var numbercode = '5702375'
let func2 = (code) => {
  let length = code.length
  let count = 0
  let result = ''
  for (let i = 0; i < length; i++) {
    let n = code[length - 1 - i]
    count += 1
    if (count === 3) {
      result = ',' + n + result
      count = 0
    } else {
      result = n + result
    }
  }
  return result
}
// test
console.log(func2(''))
console.log(func2(numbercode))
console.log(func2('0000000000000000000'))

3

var filesize = 2837475
let func3 = (bite) => {
  let kb = bite / 1024
  let mb = bite / (1024 * 1024)
  let gb = bite / (1024 * 1024 * 1024)

  if (mb <= 1) {
    return kb + 'kb'
  } else if (gb <= 1) {
    return mb + 'mb'
  } else {
    return gb + 'gb'
  }
}
// test
console.log(func3(0))
console.log(func3(1024))
console.log(func3(1025))
console.log(func3(1024 * 1024))
console.log(func3(1024 * 1024 + 1))
console.log(func3(1024 * 1024 * 1024))
console.log(func3(1024 * 1024 * 1024 + 1))

[CandyQiu]

我的蠢方法

// https://github.com/zhangxinxu/quiz/issues/42
// 2019 - 9-6

// 1
var bankCode = '6222081812002934027';
var formlist = [4,4,4,4,3];
function getFormBankCode(bankCode,formlist){
  var count = 0 ;
  var cutCode = [];
  for(var i = 0; i< formlist.length; i++ ){
    cutCode.push(bankCode.slice(count , count + formlist[i]) )
    count = count + formlist[i];
  }
  return cutCode.join(" ");
}
console.log(getFormBankCode(bankCode,formlist)) ;

// 2
var numberCode = '5702375';
console.log( (numberCode - 0 ).toLocaleString());

// 3
 var filesize = 2837475;
function getSize(filesize){
  if ( filesize / 1024  > 0 ){
    filesize = filesize / 1024;
    if( filesize / 1024  > 0) {
      filesize = filesize / 1024;
      return filesize + "G";
    }
    else{
      return filesize + "M";
    }
  }else{
    return filesize + "K";
  }
}
console.log( getSize(filesize) );

[xxf1996]

正则是个好东西啊，总觉得好多高级用法还不清楚怎么用；

var bankCode = '6222081812002934027'
var numberCode = '5702375'
var fileSize = 2837475

// 1
function bankFormat (str) {
  return str.replace(/(\d{4})/g, '$1 ')
}

// 2：正则没有逆向查找？
function moneyFormat (str) {
  const reverseString = str => str.split('').reverse().join('')
  return reverseString(reverseString(str).replace(/(\d{3})/g, '$1,'))
}

// 3：暂时没考虑小数点的取舍
function sizeFormat (num) {
  let res = ''
  const G = 1024**3
  const M = 1024**2
  const K = 1024

  if (num >= G) {
    res = num / G + 'G' 
  } else if (num >= M) {
    res = num / M + 'M'
  } else {
    res = num / K + 'K'
  }

  return res
}

console.log(bankFormat(bankCode)) // 6222 0818 1200 2934 027
console.log(moneyFormat(numberCode)) // 5,702,375
console.log(sizeFormat(fileSize)) // 2.706027030944824M

[zhangxinxu]

本期要点：

1. 这个匹配值得大家关注：bankCode.match(/\d{3,4}/g).join(' ')。然后“$&是最后匹配的字符”。
2. 数字千位分隔符表示语义会更好。<meta name="format-detection" content="telephone=no"> 这个其实不推荐的。Number(numberCode).toLocaleString()是最佳实现了。toLocaleString保留三位小数（细节可以关注下）。
3. Intl.NumberFormat： https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/NumberFormat (回头我研究整理下)
4. 最后一题要点：注意取几位小数，最好向上取，然后注意下文件大小的单位是比特。

[ziven27]

不好意思，这边错过了答题时间。不得分，但还是补齐一下我的答案：

// 第一题=============
var backCode = '6222081812002934027';
var newCode = '';
for (var i = 0, len = backCode.length; i < len; i = i + 4) {
    // 每四个分段
    newCode += ' ' + backCode.substr(i, 4);
}
// 去掉第一个空格
newCode = newCode.substr(1);
console.log(newCode);

// 第二题=============
var numberCode = '5702375';
var newNumber = '';
// 倒叙循环
for (var i = numberCode.length; i - 3 > 0; i = i - 3) {
    newNumber = ',' + numberCode.substr(i - 3, 3) + newNumber;
}
// 填充第一组
newNumber = numberCode.substr(0, i) + newNumber;

console.log(newNumber);

// 第三题=============
var filesize = 2837475;
var K = 1024;
var M = 1024 * 1024;
var G = 1024 * 1024 * 1024;
var fileString = '';
if (filesize > G - 1) {
    fileString = parseFloat(filesize / G).toFixed(2) + 'G';
} else if (filesize > M - 1) {
    fileString = parseFloat(filesize / M).toFixed(2) + 'M';
} else {
    fileString = parseFloat(filesize / K).toFixed(2) + 'K';
}

console.log(fileString);