通过一种方法供以后评估 [英] Passing a method for later evaluation

问题描述

如果我将函数作为参数传递，并且该函数是jQuery方法，以后调用传递的函数是否仍会正确设置this?我以为会，但是稍后调用该函数的是this = Window.

If I pass a function as an argument, and the function is a jQuery method, will calling the passed function later still correctly set this? I thought it would, but calling the function later has this = Window.

示例代码:

var $input = $('input').first();

var evaluators = [];

evaluators.push($input.val);

_.forEach(evaluators, function(valueMethod) {
    return valueMethod() //returns undefined always since this = window
}).

推荐答案

尝试使用 bind :

bind()方法创建一个新函数，该函数在被调用时将其关键字设置为提供的值，并在调用新函数时提供给定的参数序列.

The bind() method creates a new function that, when called, has its this keyword set to the provided value, with a given sequence of arguments preceding any provided when the new function is called.

evaluators.push($input.val.bind($input)); 

值得注意的是，bind是在旧版浏览器上不受支持(例如IE8和FF3(或更早版本).

It is worth noting bind is not supported on older browsers (e.g. IE8 and FF3 (or older)).

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