What is the use of double-layer ajax nesting

This article is to share with you about the use of double-layer ajax nesting, the editor thinks it is very practical, so I share it with you to learn. I hope you can get something after reading this article.

Double-layer ajax nesting (can be multi-layer) usage. The details are as follows:

Function addbus () {/ / clear all elements in the a tag / / $("# S1") .remove (); var chooseIdTypeOne = $("# chooseIdTypeOne2") .find ("option:selected") .val () $.ajax ({url: "/ ftcms/changeProject.do?getOriginal&OriginalName=" + chooseIdTypeOne, data: null, / / Parameter type: "post", cache: false, dataType: "json", / / return json data error: function () {/ / document.getElementById ("chooseIdTypeOnechdranone"). Options.length = 0; alert ('error');}, success:onchangecal}) } function onchangecal (data) {var chooseIdTypeOne = $("# chooseIdTypeOne2"). Find ("option:selected"). Val (); document.getElementById ("chooseIdTypeOnechdranone2"). Options.length = 0; / / clear the original option var str= "Please select" If (chooseIdTypeOne==1) {$.ajax ({url: "/ ftcms/changeProject.do?getOriginal&OriginalName=" + chooseIdTypeOne, data: null, / / Parameter type: "post", cache: false, dataType: "json", / / returns json data error: function () {/ / document.getElementById ("chooseIdTypeOnechdranone"). Options.length = 0; alert ('error');}, success:onchangecal}) } if (chooseIdTypeOne==2) {for (var item0)