快来看JS的的几个常用算法（持续更新中）

数组去重

	// 第一种方法
	let arr = [1,1,2,3,4];
	function fun(v) {
		return Array.from(new Set(v))
	}
	console.log(fun(arr)) //[1,2,3,4]
	// 第二种方法
	let qc= [...new Set(arr)]
  console.log(qc) //[1,2,3,4]

数组并集

	let arr0 = ['a','b','c'];
	let arr2 = ['c','d'];
	let a=new Set(arr0);
	let b=new Set(arr2);
	let bj = new Set([...a,...b]);
  console.log(bj);//{"a", "b", "c", "d"}

数组交集

	let jj = new Set([...a].filter(x=>b.includes(x)));
  console.log(jj);//{"c"}

数组差集

	let cj = new Set([...a].filter(x=>!b.includes(x)));
  console.log(cj);//{"a", "b"}

统计数组相同项的个数

	let arr6=['a','a','a','b','c','c'];
	let arr6obj=arr6.reduce(function(obj,name){
		obj[name]=obj[name]?++obj[name]:1;
		return obj;
	},{})
  console.log(arr6obj)// {a: 3, b: 1, c: 2}

数组方法reduce()实现filter、map

	let arr7=[2,3,10];
	const arro=arr7.reduce(function(list,num){
		num=num*2;
		if(num>=20){
			list.push(num)
		}
		return list;
	},[])
  console.log(arro);//[20]

字符串转换为数字

	let num1='1' * 1;
  console.log(typeof num1) //number

使用Boolean过滤数组中的所有假值

	let jz=[0,null,false,NaN,1,2];
	const filter1=arr1=>arr1.filter(Boolean);
  console.log(filter1(jz)) //[1,2]

取整

	let num2=1.223;
  console.log(num2|0);//1

判断奇偶

	let num3=3;
  console.log(!!(num3 & 1));//true

精确到指定位数(取小数第一位)

	let num4=6.222;
  console.log(num4.toFixed(1));//6.2

解构

	let [rr,aa]=[1,2];
  console.log(rr);//1

使用解构交换数值

	[rr,aa]=[aa,rr];
  console.log(rr);//2

判断数据类型

	let ee=[1,12];
	let ongjj={
		name:'maomin'
	}
	function isType(arr) {
    	return Object.prototype.toString.call(arr) 
	}	
	console.log(isType(ee));//[object Array]
  console.log(isType(ongjj));//[object Object]

字符串转化为对象

	let stringobj='{"id":0,"name":"张三","age":12}';
	let d3=JSON.parse(stringobj);
  console.log(d3)//{id: 0, name: "张三", age: 12}

对象转化为字符串

	let objj={
		id:0,
		name:'maomin'
	}
	let d4=JSON.stringify(objj)
  console.log(d4);//{"id":0,"name":"maomin"}

字符串转化为数组

	let stringww="a,b,c,d,e,f";
  console.log(stringww.split(","))//["a", "b", "c", "d", "e", "f"]

数组转化为字符串

	let arr9=['l','o','v','e'];
  console.log(arr9.join('-'))

去除字符串指定符号

	var stre="a,b,c,d";
	function clear(str) { 
		str = str.replace(/,/g, "");//取消字符串中出现的所有逗号 
		return str; 
	}
	console.log(clear(stre))//abcd