Breaking JavaScript execution always when cookie is set

Question

Is it possible to break javascript execution in FireBug or in some other web developer tool always when cookie is set (without setting JS breakpoints explicitly)?

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Answer 1

In Chrome dev-tools, you can right click on a cookie in the application cookies and select 'show request with this cookie'

so it's not an interception, but if your goal is to identify where a cookie comes from then it's a good way.

Answer 2

Try setting it in a If statement.

if(document.cookie.indexOf('...') >= 0){
  debugger;
}

note: when using firefox your console has to be open. in chrome this is not the case.

Answer 3

The answer below does not seem to work in Chrome. Adding this snippet in the beginning of an html → head block works fine:

<script type="text/javascript">
    function debugAccess(obj, prop, debugGet){
        var origValue = obj[prop];
        Object.defineProperty(obj, prop, {
            get: function () {
                if ( debugGet )
                    debugger;
                return origValue;
            },
            set: function(val) {
                debugger;
                return origValue = val;
            }
        });
    };
    debugAccess(document, 'cookie');
</script>

See this Angular University page for more information.

Answer 4

This should work (run it in a console):

origDescriptor = Object.getOwnPropertyDescriptor(HTMLDocument.prototype, 'cookie');
Object.defineProperty(document, 'cookie', {
  get() {
    return origDescriptor.get.call(this);
  },
  set(value) {
    debugger;
    return origDescriptor.set.call(this, value);
  },
  enumerable: true,
  configurable: true
});