交换两个变量，不使用第三个变量（js向）

Number：

var a = 1.23, b = 3.21;a = b + (b = a) * 0;    //a = 3.21  b = 1.23a = b + (b = a, 0);     //a = 1.23  b = 3.21a = Number(b, b = a);   //a = 3.21  b = 1.23

Boolean

var a = true, b = false;a = Boolean(b & (b = a, true));     //a = false  b = truea = Boolean(b, b = a);              //a = true  b = false

String:

var a = '萌萌哒', b = '么么哒';a = b + (b = a, '');    //a = '么么哒'  b = '萌萌哒'a = String(b, b = a);   //a = '萌萌哒'  b = '么么哒'

Object:

var a = {val:'萌萌哒'}, b = {val:'么么哒'};a = Object(b, b = a); //a = {val:'么么哒'}  b = {val:'萌萌哒'}