Apply and call scope

Both call and apply are intended to change the context in which a function is run, in other words, to change the direction of this within the function body. Because JavaScript functions have a concept of "context at definition" and "runtime context" and "context can be changed."

The two work exactly the same way, except that they accept the parameters differently. For example, there is a function func1 defined as follows:

var function (Arg1, arg2) {};

Can be passed Func1.call (this, arg1, arg2); Or func1.apply (this, [Arg1, arg2]); To invoke. Where this is the context you want to specify, he can have any JavaScript object (everything in JavaScript), call needs to pass the parameters in order, and apply is to put the parameters in the array.

In JavaScript, the number of parameters of a function is not fixed, so to say the applicable conditions, when your parameters are clearly known quantity, with call, but not sure, with apply, and then put the parameter push into the array to pass in. When the number of arguments is indeterminate, the function can also traverse all the arguments by arguments the array.

Apply and call scope