Basic-Interview-Questions

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• software-engineering-interview-guide/ 为繁忙的工程师提供精心访谈准备材料

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原型链

function Foo() {
  this.bar = 10
}

Foo.prototype.bar = 42

var foo = new Foo()
console.log(foo.bar)

delete foo.bar
console.log(foo.bar)

Anwser

```js 10 42 ```

[Jogiter]

JSON.stringify

let a = {y: 1}
a.x = a
JSON.stringify(a) 

what happened:

```js Uncaught TypeError: Converting circular structure to JSON ```

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typescript

unknow vs any

Any

• If the type of the variable is "any" then we can assign any type of value (string, number, boolean, etc) to the variable.
• It is similar to assigning the variable in JavaScript.
• :warning:Actually, it is not good practice to use "any" type, because using "any" throws away the type restrictions. The first reason we are using TypeScript is type safety. But the type "any" has thrown away this restriction.
• :warning:Using "any" will lead to a run time error.

Unknown

• The unknown type comes into the picture to resolve the above run time error.
• The "unknown" type introduced in TypeScript 3.0 is also considered a top type.
• It is similar to any, which means it accepts all types of values (string, number, boolean, etc.). But the difference is, if you are
• using an "unknown" type then, TypeScript is enforce the type check before using the variable.

Summary

• You can assign any values to unknown type variables, but you cannot use them before doing a type check or type assertion.
• You can assign any values to any type of variable and you can use it without type check.
• The unknown is a more recommended type than any because it provides type-safe.

public

class Car {
    constructor(public m: string, n: string) {}
}

var car = new Car('a', 'b')

compile

```js class Car { constructor(m, n) { this.m = m; } } ```

[Jogiter]

1. turing code-challenge 给定一个字符串，仅将字符串颠倒顺序，特殊字符的位置不变。 比如给定一个字符串 ab-cd，将转换成 dc-ba。ac-cd-efgh!!，将转换成 hg-fe-dcca!!

Anwser

```js function reverLet(S) { let result = '' const length = S.length let startIdx = 0 let endIdx = length - 1 let start = '' let startCode = '' let end = '' let endCode = '' let middle = '' while (startIdx < length && startIdx <= endIdx) { start = S.slice(0, startIdx) startCode = S.slice(startIdx, startIdx + 1) middle = S.slice(startIdx + 1, endIdx) end = S.slice(endIdx + 1) endCode = endIdx === length - 1 ? S.slice(endIdx) : S.slice(endIdx, endIdx + 1) if (!/[a-wA-W]/.test(startCode)) { startIdx++ } else if (!/[a-wA-W]/.test(endCode)) { endIdx-- } else { S = `${start}${endCode}${middle}${startCode}${end}` startIdx++ endIdx-- } } result = S return result } // console.log(reverLet('ab-cde-fgh!!')) console.log(reverLet('ac-cd-efgh!!')) ```