How to convert text to binary code in JavaScript?

What you should do is convert every char using charCodeAt function to get the Ascii Code in decimal. Then you can convert it to Binary value using toString(2):

HTML:

<input id="ti1" value ="TEST"/>
<input id="ti2"/>
<button onClick="convert();">Convert!</button>

JS:

function convert() {
  var output = document.getElementById("ti2");
  var input = document.getElementById("ti1").value;
  output.value = "";
  for (var i = 0; i < input.length; i++) {
      output.value += input[i].charCodeAt(0).toString(2) + " ";
  }
}

And here's a fiddle: http://jsfiddle.net/fA24Y/1/

This might be the simplest you can get:

function text2Binary(string) {
    return string.split('').map(function (char) {
        return char.charCodeAt(0).toString(2);
    }).join(' ');
}