JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdn.css.net/libs/jquery/2.2.4/jquery.min.js"></script>
<div id="sqzr">

</div>

JavaScript

var data = [1,2,3,4,5,6];

$("#sqzr").append("加载遮罩层<br/>");

function process(idx) {
		if(idx >= data.length) {
        $("#sqzr").append("ajax全部执行完成,关闭遮罩层<br/>");
        return;
    }
    
    $.ajax({
    	  url: '/echo/json/',
        method: 'get',
        beforeSend: function() {
      	    $("#sqzr").append(data[idx] + "开始执行<br/>");
        },
        success: function() {
            $("#sqzr").append(data[idx] + "执行完成<br/>");
            process(++idx);
        }
    });
}

process(0);