Override JS function from another file

Question

Im trying to override a JS function from Bigcartel. I have no access to the JS file.

The original is:

updateCart: function(cart) {
    $('aside .cart .count, .main header .cart').htmlHighlight(cart.item_count);
    return $('aside .cart .total').htmlHighlight(Format.money(cart.total, true, true));
  },

And i am trying to change it to this:

updateCart: function(cart) {
  $('aside .cart .count, .sml .cart, .big .cart .count').htmlHighlight(cart.item_count);
  return $('aside .cart .total').htmlHighlight(Format.money(cart.total, true, true));
},

I am aware that others have asked similar questions, but i am a complete noob when it comes to understanding how to implement JS (i only know how to tweek through trial and error)

If any one could be so kind as to help me out by giving me the answer that would be great.

Thanks,

iWed-

EDIT [10.10.13 :: 21:24hr]

To clarify, i do not have direct access to the original JS file. i can only view it through chrome. I only have access to html files. It is for a Big cartel theme Edit.

Here is a link to to copied JS using chrome. Line 216 is the code, if this helps : http://jsfiddle.net/w9GTJ/

If that function is accessible you can simply change it by *reference*... If it is accessible from the global object then you have no problems, otherwise it could be really hard to do — Niccolò Campolungo, Oct 10 '13 at 16:42
@LightStyle `but i am a complete noob when it comes to understanding how to implement JS ` — Rafael Herscovici, Oct 10 '13 at 16:42
@Dementic, there are a lot of reasons , IMHO, to vote to close this question, because it has no relevant code inside of it, and because it is badly described. It could be inside a closure and so inaccessible, or it could be a simple prototype function which can be easily overwritten. — Niccolò Campolungo, Oct 10 '13 at 16:46
@LightStyle sorry if i havent supplied enough information, what would you like me to add to help? i have just added a link to the copied js that is generated by bigcartel — Wednesday Man, Oct 10 '13 at 20:31
Just add `Store.cart.updateCart = function(cart) {/*your code here*/};` after the external script loaded completely. — Niccolò Campolungo, Oct 10 '13 at 20:49

Tibos · Accepted Answer · 2015-05-27T17:56:34.153

EDIT: You are in luck. From the posted code you can see that the updateCart method is exported on the window.Store global object. The solution is to add this code after the original script loaded:

window.Store.updateCart = function(cart) {
  $('aside .cart .count, .sml .cart, .big .cart .count').htmlHighlight(cart.item_count);
  return $('aside .cart .total').htmlHighlight(Format.money(cart.total, true, true));
};

Explanation for a general situation:

All scripts loaded in a web page run in the same global scope, so overwriting a variable is as simple as inserting your script afterwards:

<script>
var x = 5; // original script
</script>
<script>
x = 2; // your inserted script
</script>

From the looks of it, your function is defined as property of an object:

var x = {
   updateCart : function(cart) {
     // stuff
   }
}

So to overwrite it you need to do:

x.updateCart = function(cart) {
  // your code
}

Finally, there is one situation where you simply can't overwrite it, if function is private in the original code:

function() {
   var x = {
      updateCart: function(){}
   }
}()

// No way to access x.updateCart here

sorry about the late reply - i got held up. It says im missing a ; before the statement, why ? — Wednesday Man, Oct 19 '13 at 23:55

score 0 · Answer 2 · answered Oct 10 '13 at 16:45

0

Assuming you're able to find and access corresponding js object:

[theTargetObject].prototype.updateCart= function(cart) {
          $('aside .cart .count, .sml .cart, .big .cart .count').htmlHighlight(cart.item_count);
          return $('aside .cart .total').htmlHighlight(Format.money(cart.total, true, true));
}

answered Oct 10 '13 at 16:45

fmgp

1,638
17
17

This simply doesn't work. The prototype property is only used on constructors and there is no indication that theTargetObject is a constructor. – Tibos Oct 10 '13 at 16:51

Override JS function from another file

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