The promise of jquery

We all have this demand:

I need a few AJAX requests and the data is all successfully fetched before it can be loaded.

Previous practice:

1, nesting in the success callback, which makes the code difficult to read.

2, asynchronous synchronous, sequential execution, not in line with the original purpose of Ajax, efficiency is not high.

3, write a callback function, statistics all requests are completed after execution. Seems a bit cumbersome.

jquery now provides such a feature.

$.when ($.ajax (URL1)

, $.ajax (URL2))

. Then (function success (ARG1,AGR2) {

ARG1[0],ARG2[0] is the data returned by two requests

},function error (ERR) {

});