search

CPPAlien / JS-QA

前端知识问答
0 stars 0 forks source link

with 语句 #38

Open CPPAlien opened 4 years ago

CPPAlien commented 4 years ago 
var obj = {
    a: 1,
    b: 2,
    c: 3
};
obj.a = 2;
obj.b = 3;
obj.c = 4;

| v

with (obj) {
    a = 3;
    b = 4;
    c = 5;
}
CPPAlien commented 4 years ago

缺点：影响全局变量


const obj = {a: 1, b: 2}
console.log(obj)

with(obj) {
    console.log(a)
    c = 3
    a = 2
}

console.log(c)   // 3
console.log(a)  // a is not defined

性能差