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
