[英]Function not showing correct result
我已经写了这段代码
var foo = {
x:2,
baz: {
x:1,
bar:function() {
return this.x;
}
}
}
var go = foo.baz.bar;
console.log(go());
答案是不确定的。 但为什么? 当go
映射到功能bar
,它应该返回2
因为foo
有x:2
。
正如Tushar在评论中所说,要回答这个问题:
该上下文取决于函数的调用方式
这是一个片段,说明使用bind
, call
或apply
实现您想要的内容的一些方法
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
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