jQuery.ajax多任务异步转同步示例

let tasks = []; //任务列表
let counter = 0; //计数器

//任务
let todo = function(){
	if(counter<tasks.length){
		$.ajax({
			url: "/test.ashx",
			data: "task=" + tasks[counter],
			async: true,
			success: function(data){
				console.log(data);
			},
			error: function(){
				console.log("error.");
			},
			complete: function(){
				console.log(counter, tasks.length);
				counter++;
				todo();
			}
		});
	}else{
		console.log("finish.");
	}
}

//初始化任务列表和计数器，开始任务
$("#btn").click(function(){
	tasks = ["task1", "task2", "task3"];
	counter = 0;
	todo();
});