this is a keyword in JavaScript. It refers to an internal object created automatically when a function executes, it can only be used in a function. For example:        function test(){　　　　this.x = 1;　　}The this keyword will change when a function is called in different situations. However, the general rule is : this refers to the object which calls the function.Next we discuss the use of this in 4 different situations.1. In pure function callThis is the most common use of a function, it is a global call, so the this w...