++单独使用的时候都会自增(放在前面和后面都一样)
++放前面先自增,后运算
++放后面先运算,后自增
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/*
++单独使用的时候都会自增(放在前面和后面都一样)
++放前面先自增,后运算
++放后面先运算,后自增
*/
var a = 10;
var c = 20;
b = ++a +2;
d = c++ +3;
console.log(b);//13
console.log(a);//11
console.log(d);//23
console.log(c);//21
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