A simple summary of promise in JS (ES6)

For example:

Use the callback function:

After using the Promise object:

Promise function: The callback function is separated out, after the execution of the asynchronous operation, with a chain call method to execute the callback function, for the multi-level callback, it is very convenient.

Let's look at the following example:

At this point the console will output the result of ' AA '

At this point the console still has only ' AA ' results

At this point the console will have ' AA ' and ' BB ' results.

In other words, the return function is written in then, chained to the call, separated. The code looks more clear.

Not finished, to be summarized.

A simple summary of promise in JS (ES6)