The method and difference summary of synchronous and asynchronous processing in JS

  To process the results of sending requests after using AJAX requests, it is best to use synchronization requests, here is a brief introduction to the next JS synchronous and asynchronous processing methods and differences, interested friends do not miss

When using an asynchronous request, sometimes it is necessary to return the result of the asynchronous request to another JS function, in which case there will be an asynchronous request return request result, the request is in the JS function has performed the subsequent operation, that is, has been executed, which will cause the return result is null character.     Summary: To process the results of a send request after using an AJAX request, it is best to use a synchronization request.     For example: The following example shows an incorrect return result because the Ajax asynchronous request has not been executed and the function has been returned,    code is as follows: the function fn () {    var result = "";    $.ajax ({  url: ' Your URL ',  data:{name:value},  cache:false,  async:tr ue,  type: "POST",  success:function (data) {  do something....    result = .... }   //processing of data returned in Ajax, error     return result; }    1 Asynchronous request mode:    code is as follows: $.ajax ({&N Bsp URL: ' Your URL ',  data:{name:value},  cache:false,  async:true,  type: ' POST ',  dataType: ' Json/xml/html ',  success:function (Result) {  do something.... } });    2 Synchronous request mode   generation Code as follows: $.ajax ({  url: ' Your URL ',  data:{name:value},  cache:false,  async:false,  type: "POST",  dataType: ' json/xml/html ',  success:function (Result) {  do something.... } }) ;