How to make onChange work properly in FancyGrid?

I am using Fancy Grid, when ever some changes or update occurs in this cell I want to see it inside debugger, I have put debugger inside function and when I make any changes it does not pause inside this function nor it print anything in console. Please find the code below:

  {                    index: 'fieldLength',                    editable: editableLength,                    title: 'Field Length',                    flex: 1,                    headerCls: 'header-cell-without-search-input',                    filter:{                        header:true                    },                    type: 'number',                    vtype: {                        before: ['notempty', 'notnan'],                        type: 'min',                        param: 0                    },                    events: [{                        onchange : function (g,o) {                            debugger                            console.log("SOmething changed!!")                        }                    }]                }

What is the proper solution here?

I have try many methods like before|after , update, save but still not found an proper solution.