code: function createShaderFromScript(
      gl, scriptId, opt_shaderType, opt_errorCallback) {
    let shaderSource = "";
    const shaderScript = getElementById(scriptId);
    if (!shaderScript) {
      throw "*** Error: unknown script element" + scriptId;
    }
    shaderSource = shaderScript.text;
  
    const shaderType = opt_shaderType || getShaderTypeFromScriptType(gl, shaderScript.type);
    if (!shaderType) {
      throw "*** Error: unknown shader type";
    }
  
    return loadShader(gl, shaderSource, shaderType, opt_errorCallback);
  }
docs: Loads a shader from a script tag.
  @param {WebGLRenderingContext} gl The WebGLRenderingContext to use.
  @param {string} scriptId The id of the script tag.
  @param {number} [opt_shaderType] The type of shader. If not passed in it will
  be derived from the type of the script tag.
  @param {module:twgl.ErrorCallback} [opt_errorCallback] callback for errors.
  @return {WebGLShader?} The created shader or null if error.
  @private