Loading different video (html5) quality according to screen resolution

Question

Im trying to display different video resolution according to the users screen height resolution, i have this code but im not an expert with javascript. It's supposed to change the src attribute, if the res is lower o equal to 360px height, and so on. Any suggestions?

 <script type="text/rocketscript"> var v = new Array(); v[0] = ["https://dl.dropboxusercontent.com/u/51626189/nli-vids/intro/intro-360_x264.mp4"]; v[1] = ["https://dl.dropboxusercontent.com/u/51626189/nli-vids/intro/intro-480_x264.mp4"]; v[2] = ["https://dl.dropboxusercontent.com/u/51626189/nli-vids/intro/intro-720_x264.mp4"]; v[3] = ["https://dl.dropboxusercontent.com/u/51626189/nli-vids/intro/intro-1080_x264.mp4"]; function changeVid(n){ var video = document.getElementById('video'); if (screen.height<=360) {video.setAttribute("src", v[n][0]);} else if (screen.height<=480) {video.setAttribute("src", v[n][1]);} else if (screen.height<=720) {video.setAttribute("src", v[n][2]);} else if (screen.height<=768) {video.setAttribute("src", v[n][2]);} else if (screen.height<=1080) {video.setAttribute("src", v[n][3]);} else if (screen.width>=1920) {video.setAttribute("src", v[n][3]);} video.load();} </script> 

 <video id="video" autoplay preload src="#"> </video> 

Answer 1

I don't know about "text/rocketscript" (something to do with Wordpress and/or CloudFlare?), but this Javascript works:

<script type="text/javascript">
var v = new Array();
v[0] = "https://dl.dropboxusercontent.com/u/51626189/nli-vids/intro/intro-360_x264.mp4";
v[1] = "https://dl.dropboxusercontent.com/u/51626189/nli-vids/intro/intro-480_x264.mp4";
v[2] = "https://dl.dropboxusercontent.com/u/51626189/nli-vids/intro/intro-720_x264.mp4";
v[3] = "https://dl.dropboxusercontent.com/u/51626189/nli-vids/intro/intro-1080_x264.mp4";

function changeVid() {
    var video = document.getElementById('video');
    if (screen.height <= 360) video.setAttribute("src", v[0]);
    else if (screen.height <= 480) video.setAttribute("src", v[1]);
    else if (screen.height <= 768) video.setAttribute("src", v[2]);
    else video.setAttribute("src", v[3]);

    video.load();
}

changeVid();
</script>

Sorry, I can't get it to work as a snippet, JS Fiddle here instead: http://jsfiddle.net/3g59yomb/

Note that it loads a high-res video (on my system with a 2560 x 1440 screen) even though my browser window is much smaller, and the JS Fiddle frame even smaller still. That may or may not be a bug! But it does load a video.