If you need to run a debugger to find a place where some property is changed you can redefine this property as a function and add 'debugger' line
For example:
For example:
// There you will be able to find a place // where 'document.getElementById('qty').value' is changed ( function(obj){ // var obj = document.getElementById('qty'); obj._value = obj.value; Object.defineProperty(obj, 'value', { get: function () { return obj._value; }, set: function (value) { debugger; // sets breakpoint obj._value = value; } }); } )(document.getElementById('qty'))