功能未顯示正確的結果

Question

我已經寫了這段代碼

var foo = {
    x:2,
    baz: {
        x:1,
        bar:function() {
            return this.x;
        }
    }
}

var go = foo.baz.bar;
console.log(go());

答案是不確定的。 但為什么？ 當go映射到功能bar ，它應該返回2因為foo有x:2 。

Answer 1

正如Tushar在評論中所說，要回答這個問題：

該上下文取決於函數的調用方式

這是一個片段，說明使用bind ， call或apply實現您想要的內容的一些方法

 var foo ={ x:2, baz: { x:1, bar:function() { return this.x; } } }; var go = foo.baz.bar; console.log("go(): " + go()); //this === window, window.x is undefined console.log("go.bind(foo)(): " +go.bind(foo)()); //this === foo, foo.x is 2 console.log("go.bind(foo.baz)(): " +go.bind(foo.baz)()); //this === foo.baz, foo.baz.x is 1 console.log("go.apply(foo): " + go.apply(foo)); //2 console.log("go.apply(foo.baz): " + go.apply(foo.baz)); //1 console.log("go.call(foo): " + go.call(foo)); //2 console.log("go.call(foo.baz): " + go.call(foo.baz)); //1 var x = 100; console.log(go()); //100, since window.x == 100