Question

I saw a style that use

var test = function() {
    var that = this;
    this.show() {
        that.***；
    }
}

I am wondering why use that in the function?

Answer 1

The purpose of using that is to capture this in the context in which the function was constructed. When the function is called, this is in a different context (The caller I believe) so that when test() is called, this would not be what you expected it to be (unless you understand JavaScript, in which case it would be what you expect it to be, but not what you want it to be).