javascript - What is the reasoning behind declaring var that = this; in javascript?

Question

I came across this many times in a new code base that I'm looking at and was wondering is there is any proper reasoning behind it?

Answer 1

您可以使用var that = this;is 命令保留对当前this对象的引用，稍后this将指向其他对象。

示例（取自此处）：

$('#element').click(function(){
    // this is a reference to the element clicked on

    var that = this;

    $('.elements').each(function(){
        // this is a reference to the current element in the loop
        // that is still a reference to the element clicked on
    });
});

Answer 2

有时this，JavaScript 中的含义会根据作用域而变化。 this构造函数内部的含义与this函数内部不同。这是一篇关于它的好文章。

Answer 3

如果您想在特定函数调用范围之外/内部访问“this”，其中“this”可能已更改。只是我能想到的一个例子。