var a = 20;
var b = --a + 2;
console.log(a);//19
console.log(b);//21先執(zhí)行減法操作再賦值
var a = 20;
var b = a-- + 2;
console.log(a);//19
console.log(b);//22先賦值再執(zhí)行減法操作
var a = 20;
var b = --a + 2;
console.log(a);//19
console.log(b);//21先執(zhí)行減法操作再賦值
var a = 20;
var b = a-- + 2;
console.log(a);//19
console.log(b);//22先賦值再執(zhí)行減法操作