根据2019年 新个税政策计算，实现 每月个人应缴纳 个人所得税

[erbing]

/* 
 * 根据2019年 新个税政策计算，每月个人应缴纳 个人所得税
 * e.g.
 * // 年收入
 * const yearIncome = [36000, 144000, 300000, 420000, 660000, 960000]
 * // 对应不同阶段的税率
 * const newTax = [3, 10, 20, 25, 30, 35, 45]
 * 
 * 是否有 专项扣除
 * const  deduct = []
 * 
 * calculateTax(salary, deductType)
 * 
 * salary: 月薪
 * deductType： 专项扣除类型，如果无 则为 0
 */

 // 专项扣除 amount 代表每月 金额

const  deduct = [
    {
        name: '子女教育',
        type: 1,
        amount: 1000
    },
    {
        name: '继续教育',
        type: 2,
        amount: 400
    },
    {
        name: '住房贷款利息',
        type: 3,
        amount: 1000
    },
    {
        name: '住房租金',
        type: 4,
        amount: 1500
    },
    {
        name: '赡养老人',
        type: 5,
        amount: 2000
    },
    {
        name: '大病医疗',
        type: 6,
        amount: 6000
    }
]

 const calculateTax = (salary, deductType) => {
    // todo
 }

[ali-shi]

const calculateTax = (salary, deductType,month =12 ) => { // todo

// 计算所交金额的级别
const returnLevel = (acc)=>{
    let level = 1;
    if(acc <= 36000 ){
        level=1;
    } else if (acc <= 144000 ) {
        level=2;
    } else if (acc <= 300000 ) {
        level=3;
    } else if (acc <= 420000 ) {
        level=4;
    } else if (acc <= 660000 ) {
        level=5;
    } else if (acc <= 960000 ) {
        level=6;
    } else {
        level=7;
    }
    return level;
}
// 计算所交税金
const calcSalary = (amount, level)=>{
    let newTax = {
        1:{
            rate:3,deduction:0,level:1
        },
        2:{
            rate:10,deduction:2520,level:2
        },
        3:{
            rate:20,deduction:16920,level:3
        },
        4:{
            rate:25,deduction:31920,level:4
        },
        5:{
            rate:30,deduction:52920,level:5
        },
        6:{
            rate:35,deduction:85920,level:6
        },
        7:{
            rate:45,deduction:181920,level:7
        }
    }
    return newTax[level].rate / 100 * amount - newTax[level].deduction;
}
/**
 * [description]
 * @param    {[type]}                 m      [工资]
 * @param    {[type]}                 n      [几个月]
 * @param    {[type]}                 salary [专项扣除金额]
 * @return   {[type]}                        [description]
 */
const calcAmount = (m,n,salary)=>{
    return new Array(n).fill(m).reduce( (acc,next) =>{
        acc += Number(next) - salary -5000;
        return acc;
    },0);
}
/**
 * [description]
 * @param    {[type]}                 type [专项扣除类型]
 * @return   {[type]}                      [金额]
 */
const calcDeduct = (type)=>{
    let salary = 0;
    let deduct = {
        1:{
            name: '子女教育',
            type: 1,
            amount: 1000
        },
        2:{
            name: '继续教育',
            type: 2,
            amount: 400
        },
        3:{
            name: '住房贷款利息',
            type: 3,
            amount: 1000
        },
        4:{
            name: '住房租金',
            type: 4,
            amount: 1500
        },
        5:{
            name: '赡养老人',
            type: 5,
            amount: 2000
        },
        6:{
            name: '大病医疗',
            type: 6,
            amount: 6000
        }
    }
    if( Array.isArray(type) ){
        type.map(item=>{
            salary += deduct[item].amount;
        })
    } else if(typeof type === 'number'){
        salary = deduct[type].amount;
    }
    return salary;
}
let deduct = calcDeduct(deductType);
let result = calcAmount(salary,month,deduct);
let level = returnLevel(result);
return calcSalary(result, level);   

} console.log(calculateTax(10000,[1,2,3]));