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)?

document.cookie = '...';

Harri

Answer 1

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
});

Answer 2

https://stackoverflow.com/a/41247745/2158271 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 3

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.