JavaScript如何更改函数内的参数？

Question

这是我的代码:

function makeCounter(x) {
    x = x || 0;
    var obj = {
        value: x,
        increment: function(){
            x = x + 1;
            return x;
        },
        decrement: function() {
            x = x - 1;
            return x;
        }
    }
    return obj;
} 
var counter = makeCounter();

console.log(counter.increment()); // output is 1
console.log(counter.value); // output is 0

现在,我想知道如何编辑代码,以便在counter.increment()之后值为1.

Answer 1

您需要在增加或减少后更新值,并使用this.value而不是x变量.

function makeCounter(value = 0) {
    return {
        value,
        increment () {
            return ++this.value;
        },
        decrement () {
            return --this.value;
        }
    };
} 

let counter = makeCounter();

console.log(counter.increment()); // output is 1
console.log(counter.value); // output is 1