Loading shaders from HTML script tags

From The WebGL Cookbook

This code (originally by Vladimir Vukićević) allows you to load shaders from HTML script tags like this:

<script id="shader-fs" type="x-shader/x-fragment">
  void main(void) {
    gl_FragColor = vec4(1, 1, 1, 1);
  }
</script>

Here's the code:

function getShader(gl, id) {
    var shaderScript = document.getElementById(id);
    if (!shaderScript) {
      return null;
    }
 
    var str = "";
    var k = shaderScript.firstChild;
    while (k) {
      if (k.nodeType == 3) {
        str += k.textContent;
      }
      k = k.nextSibling;
    }
 
    var shader;
    if (shaderScript.type == "x-shader/x-fragment") {
      shader = gl.createShader(gl.FRAGMENT_SHADER);
    } else if (shaderScript.type == "x-shader/x-vertex") {
      shader = gl.createShader(gl.VERTEX_SHADER);
    } else {
      return null;
    }
 
    gl.shaderSource(shader, str);
    gl.compileShader(shader);
 
    if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
      alert(gl.getShaderInfoLog(shader));
      return null;
    }
 
    return shader;
  }