[转]ES6数组:两个数组或数组对象取并集、交集、差集

1取并集

取并集
let a=new Set([1,2,3,4,5]);
let b=new Set([1,2,3,4,5,6,7,8,9]);
let arr = Array.from(new Set([...a, ...b]));
console.log('arr',arr);

结果

image.png

2 取交集

let a=new Set([1,2,3,4,5]);
let b=new Set([1,2,3,4,5,6,7,8,9]);
let arr = Array.from(new Set([...b].filter(x => a.has(x))));

结果

image.png

3 取差集

let a=new Set([1,2,3,4,5]);
let b=new Set([1,2,3,4,5,6,7,8,9]);
let arr = Array.from(new Set([...b].filter(x => !a.has(x))));
console.log('arr',arr);

结果

image.png

数组对象

1取交集

let a=[{id:1,a:123,b:1234},{id:2,a:123,b:1234}];
let b=[{id:1,a:123,b:1234},{id:2,a:123,b:1234},{id:3,a:123,b:1234},{id:4,a:123,b:1234}];
let arr = [...b].filter(x => [...a].some(y => y.id === x.id));
console.log('arr',arr)

结果

image.png

2 取差集 （这个比较好用！！！！）

let a=[{id:1,a:123,b:1234},{id:2,a:123,b:1234}];
let b=[{id:1,a:123,b:1234},{id:2,a:123,b:1234},{id:3,a:123,b:1234},{id:4,a:123,b:1234}];
let arr = [...b].filter(x => [...a].every(y => y.id !== x.id));
console.log('arr',arr);

结果

image.png

image.png

//保留n位小数并格式化输出（不足的部分补0）
var fomatFloat = function(value, n) {
    var f = Math.round(value*Math.pow(10,n))/Math.pow(10,n);
    var s = f.toString();
    var rs = s.indexOf('.');   
    if (rs < 0) {     
        s += '.';   
    } 
    for(var i = s.length - s.indexOf('.'); i <= n; i++){
      s += "0";
    }
    return s;
}
https://www.cnblogs.com/NazLee/p/11646023.html

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https://www.cnblogs.com/fei-H/p/11359028.html

原文地址 https://www.jianshu.com/p/20523688cbee