为什么这不是允许内部函数访问外部函数变量的闭包？

Question

How do I enable access to variable 'e' in funcB via a closure? 如何通过闭包启用对funcB变量'e'的访问？

<!DOCTYPE HTML>
<html>
<head>
<script>
Test = function () {};
Test.prototype.funcA = function (k)  {
    var that = this;
    return  function(e) {
        window.console.log('k: ' + k); // 'abc'
        window.console.log('e: ' + e); // 'def'
        that.funcB(k);
    };
};
Test.prototype.funcB = function (p) {
    window.console.log('p: ' + p); // 'abc'
    window.console.log('e: ' + e); // undefined (why?)
}
obj = new Test();
(obj.funcA('abc'))('def');
</script>
</head>
<body>
</body>
</html>

I'm confused about closures. 我对闭包感到困惑。

Since variable e exists in funcA (printed 'def'), why can funcB not access it since funcB is executed by funcA? 由于变量e存在于funcA（打印为'def'）中，由于funcB由funcA执行，为什么funcB无法访问它？ How do I give funcB access to variable e? 如何授予funcB访问变量e？

I want variable e to be accessible via a closure. 我希望可以通过闭包访问变量e。 I don't want to store it on the instantiated object (which I know I could do). 我不想将其存储在实例化的对象上（我知道我可以做到）。

Answer 1

You'll have to pass the value of "e" to the other function as a parameter. 您必须将“ e”的值作为参数传递给另一个函数。 Scoping in JavaScript is determined by the lexical relationship of functions, not the dynamic relationship. JavaScript中的作用域是由函数的词法关系而不是动态关系确定的。 Code in a function can see "outwards", and moving out from funcB() does not encounter a scope with "e" defined. 函数中的代码可以看到“向外”，并且从funcB()移出不会遇到定义了“ e”的范围。 The only symbols visible to code in funcB() are its own local symbols ( p in this case) and global symbols. funcB()中唯一可见的符号是它自己的局部符号（在这种情况下为p ）和全局符号。

Now, you could explicitly stash a copy of "e" on the object itself as a property: 现在，您可以显式地将对象“ e”的副本存储为属性：

return  function(e) {
    window.console.log('k: ' + k); // 'abc'
    window.console.log('e: ' + e); // 'def'

    that.e = e;
    return that.funcB(k);
};

Test.prototype.funcB = function (p) {
    window.console.log('p: ' + p); // 'abc'
    window.console.log('e: ' + this.e);
}

为什么这不是允许内部函数访问外部函数变量的闭包？

问题描述

1 个解决方案

解决方案1
1 已采纳 2014-03-17 17:39:35

为什么这不是允许内部函数访问外部函数变量的闭包？

问题描述

1 个解决方案

解决方案1 1 已采纳 2014-03-17 17:39:35

解决方案1
1 已采纳 2014-03-17 17:39:35