JavaScript前端开发时数值运算的小技巧

const ThousandNum = num => num.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ",");
const money = ThousandNum(20190214);
// money => "20,190,214"

const num1 = ~~ 1.69;
const num2 = 1.69 | 0;
const num3 = 1.69 >> 0;
// num1 num2 num3 => 1 1 1

const num1 = +null;
const num2 = +"";
const num3 = +false;
const num4 = +"169";
// num1 num2 num3 num4 => 0 0 0 169

const RoundNum = (num, decimal) => Math.round(num * 10 ** decimal) / 10 ** decimal;
const num = RoundNum(1.69, 1);
// num => 1.7

const arr = [0, 1, 2];
const min = Math.min(...arr);
const max = Math.max(...arr);
// min max => 0 2

const obj = {};
const flag = DataType(obj, "object") && !Object.keys(obj).length;
// flag => true

function DataType(tgt, type) {
 const dataType = Object.prototype.toString.call(tgt).replace(/\[object (\w+)\]/, "$1").toLowerCase();
 return type ? dataType === type : dataType;
}
DataType("liner"); // "string"
DataType(2020630); // "number"
DataType(true); // "boolean"
DataType([], "array"); // true
DataType({}, "array"); // false

const _arr = [0, 1, 2];
const arr = [..._arr];
// arr => [0, 1, 2]

const arr1 = [0, 1, 2];
const arr2 = [3, 4, 5];
const arr = [...arr1, ...arr2];
// arr => [0, 1, 2, 3, 4, 5];

const arr = [...new Set([0, 1, 1, null, null])];
// arr => [0, 1, null]

const arr = [...new Set([0, 1, 1, null, null])];
// arr => [0, 1, null]

let a = 0;
let b = 1;
[a, b] = [b, a];
// a b => 1 0

const _obj = { a: 0, b: 1, c: 2 }; // 以下方法任选一种(本人偏爱第一种，简单明了，与克隆数组几乎一样)
const obj = { ..._obj };
const obj = JSON.parse(JSON.stringify(_obj));
// obj => { a: 0, b: 1, c: 2 }

const obj1 = { a: 0, b: 1, c: 2 };
const obj2 = { c: 3, d: 4, e: 5 };
const obj = { ...obj1, ...obj2 };
// obj => { a: 0, b: 1, c: 3, d: 4, e: 5 }