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.