I have recently optimized the front end and took a look at jquery then
Found a little better packaged.
$.ajax({url:'Abc',success:function(data){
console.log(data);
}}).then(function(data){
console.log("then="+data);
return $.ajax({url:'Aaa',success:function(data){
return data;
}})
}).then(function(data){
console.log("then3="+data);
}).done(function(data){
console.log("done="+data);
}).then(function(data){
console.log("then4="+data);
})
That is to say, you don't need to call the sublayer, you can use the chain structure, which is very convenient.