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Promise processing instance that completes multiple interdependent asynchronous requests
Promise processing instance that completes multiple interdependent asynchronous requests
The following editor will bring you an article on promise processing of multiple interdependent asynchronous requests (explanation with examples). The editor thinks it’s pretty good, so I’ll share it with you now and give it as a reference. Let’s follow the editor and take a look
In projects, we often encounter multiple asynchronous requests that depend on each other. If there are three ajax requests a, b, and c, b needs to rely on the data returned by a, and c needs the data returned by a and b requests. It is naturally not advisable to use nested requests. It makes the code difficult to maintain and there are many requests. Many questions will arise.
Promise is to solve the problem of multiple asynchronous requests. Promise is an object provided by ES6, used to deliver messages for asynchronous operations.
Promise has three states: Pending (in progress), Resolved (completed, also known as Fulfilled) and Rejected (failed).
Upload the code directly. There are requests for a and b, and b depends on the request data of a. As follows:
function a(){
return new Promise(function(res,rej){
$.ajax({
url:"a",
type: "GET",
async:true,
dataType:"json",
success:function(data){
console.log(data,"a");
res(data);
}
})
});
}
function b(data){
console.log(data,"data");
return new Promise(function(res,rej){
$.ajax({
url:"b",
type: "POST",
async:true,
data:JSON.stringify(data),
dataType:"json",
success:function(data){
console.log(data,"b");
res();
}
})
});
}
$("#btn").click(function(){
a().then(function (data){
b(data);
}).then(function(){
})
})I found one on the Internet for the interface url. You can see the running results:
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