Several pit ajax callback

In the front-end development, often use ajax interface to back-end data get returned, several ajax callback summary of frequently asked questions for your reference climb pit.

1. Undefined contentType, may cause garbled data passed in the background, you can add the following code in ajax request contentType:'application/json;charset=UTF-8',
2. Good agreement reached back and return the data type of the background, the general definition json type.

    JSON.stringify():将一个JavaScript值(对象或者数组)转换为一个 JSON字符串
    JSON.parse():将一个 JSON 字符串转换为对象

Both are commonly used json api conversion

1. In the success or error correction, return is get value, even if changing the async: false can not get to see the example below:

function checkUserTask(taskid){
        $.ajax({
            method:'get',
            url:URL.checkUserTask,
            async:false,
            data:{'id':taskid},
            success:(response)=>{
                console.dir(response)
                if(response.code==200 ){
                    return true;
                }else{
                   return false;
                }
            }
        });
    }

Even if such an approach is success or failure, when calling checkUserTask methods are returned undefined, get true or false identity, it is generally written by the following:

function checkUserTask(taskid){
        var flag = false;
      
        $.ajax({
            method:'get',
            url:URL.checkUserTask,
            async:false,
            data:{'id':taskid},
            success:(response)=>{
                if(response.code==200 ){
                    flag = true;
                }else{
                    flag = false;
                }
            }
        });
        return flag;
    }

Behind the return of the callback can get the return value.