code: function getShader(gl, source, isVertex) {
    var shader = gl.createShader(isVertex ? gl.VERTEX_SHADER : gl.FRAGMENT_SHADER);
    gl.shaderSource(shader, source);
    gl.compileShader(shader);
  
    // See if it compiled successfully
  
    if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
      alert("An error occurred compiling the shaders: " + gl.getShaderInfoLog(shader));
      return null;
    }
  
    return shader;
  }
docs: getShader  Loads a shader program