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Editorial Team
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Asked: 2026-05-13T06:19:51+00:00

I’ve built a working page with lots of javascript. The javascript is placed in

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I’ve built a working page with lots of javascript. The javascript is placed in between the <head></head> tags without a problem, but I really want to move it an external file.

I though I would be able to simply cut and paste all the code minus <script></script> tags but incuding $(document).ready(function() { }); it into a .js file and reference it in the usual way, but it’s causing me big headaches. Can anyone suggest why I can’t just do this?

As a compromise, I though I would detach at least some of my functions and put them in an external file but there are problems there too. 

function look(){
  var word_id = $(this).attr("id");  
  //    Other stuff
  var   value = $(this).val();  
  //    Other stuff
}

$("input").focus(function(){look();});

In the above function, this is not the this it used to be when the code looked like this:

$("input").focus(function(){
  var word_id = $(this).attr("id");  
  //    Other stuff
  var   value = $(this).val();  
  //    Other stuff
});

I hope that a really clever person will spot my errors easily. Many thanks, Patrick.

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1 Answer

  1. Editorial Team

    When you call a function with no context specified, as you are calling look(), the this keyword inside that function will be the global object.

    In your case you could only pass a reference to your function, and it will work properly:

    $("input").focus(look);

    Also, it might be helpful to know that the this keyword is not completely implicit, can be set explicitly by using the call and apply functions:

    function test(arg1){
  alert(this + arg1);
}

test.call('hello ', 'world'); // will alert 'hello world'

    And that the context (the this keyword) is set implicitly in the following cases:

    1- When calling a function that is member of an object, eg.:

    obj.myFunc(); // 'this' will refer to obj

    2- When calling a function with the new operator:

    var test = new Func(); // 'this' will refer to a new object

    3- When calling a function not associated with any object:

    foo();
// or
(function () {})(); // 'this' will be the global object
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