// A simple that sets the color style of its context
  function changeColor( color ) {
      this.style.color = color;
  }
  
  // Calling it on the window object, which fails, since it doesn't
  // have a style object
  changeColor( "white" );
  
  // Find the element with an ID of main
  var main = document.getElementById("main");
  
  // Set its color to black, using the call method
  // The call method sets the context with the first argument
  // and passes all the other arguments as arguments to the function
  changeColor.call( main, "black" );
  
  // A function that sets the color on  the body element
  function setBodyColor() {
      // The apply method sets the context to the body element
      // with the first argument, the second argument is an array
      // of arguments that gets passed to the function
      changeColor.apply( document.body, arguments );
  }
  
  // Set the background color of the body to black
  setBodyColor( "black" );