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 The role of call, apply, and bind is to change the context of function execution, and when they are used, they will change the this pointing to when the function is running. call, apply, and bind are all methods under Function.prototype, which are used to change the runtime context of the function. The final return value is the return value of the method you called. If the method has no return value, it returns undefined.

 Functions and methods are an important knowledge point in programming. The key point of a function is how to call and execute. The way it is called has a huge impact on how the code inside the function is executed, especially in the creation of the this parameter. In addition to the most basic calling method such as function name (), what other methods are there? The following briefly introduces the three most basic (excluding, bind, apply, call).

 Generators are a new function control and usage scheme in ES6 that gives you more control over how functions continue, pause, and more. We usually write a lot of functions, and the conditions for these functions to terminate are usually return values or exceptions. Generator functions are also functions, but with a few differences from regular functions. First, generator functions should add the symbol "*" after the function. The generator function can then use the yield keyword to control the execution. Finally, the return value of a generator function is a generator. A generator is actually a special kind of iterator.