JSFiddle - React, Tailwind, and code Playground

JavaScript

var json = 
{
	"data": [
		{
			"sort": ["20150707144529", "incoming1.mp4"]
		},
		{
			"sort": ["20150707144530", "incoming2.mp4"]
		},
		{
			"sort": ["20150707144524", "incoming3.mp4"]
		}
	]
};

var max = 0;
var maxIndex = 0;

for (var index = 0; index < json.data.length; index++) {
    var val = parseInt(json.data[index].sort[0]);
    if (val > max) {
        max = val;
        maxIndex = index;
    }
}

alert('highest is ' + json.data[maxIndex].sort[1]);