Custom eventemmiter in range ionic-angular component is not working on production

Ionic Framework ionic-v3
1

Hi evereyone,

I put an eventemitter inside of /node_modules/ionic-angular/components/range/range.js file like this:

Range.prototype._pointerDown = function (ev) {
        if (this._disabled) {
            return false;
        }

        //Emit ion start event to run the timer for collecting of slider move
        this.ionStart.emit(this);
        .
        .
        .
        .
        
    };

This code works fine in debug mode and when i run on android device, but when I build a production release, this isn’t work and no event wasn’t fired!!!

Any help will be appreciated.