JSFiddle - React, Tailwind, and code Playground

HTML

<script src="//cdnjs.cloudflare.com/ajax/libs/underscore.js/1.7.0/underscore-min.js"></script>
<pre id="output">
</pre>

JavaScript

var postData = [{label:"test1", "data": [ {X: "10", Y:"11"}, {X: "12", Y: "13"}] }];

var data = []

$.each(postData, function (key, value) {
    data.push({
        label: value.label,
        data: _(value.data).map(function(innerVal) {
           var arr = new Array();
           arr.push(innerVal.X);
           arr.push(innerVal.Y);
           return arr;
        })
      })
    });

var str = JSON.stringify(data, undefined,  2);
$("#output").html(str);