javascript - Extending MomentJS to override toString() function -

i'm trying extend moment's tostring function return date in different format.

i.e. want create momentdate below:

// return "sat dec 12 2015 00:00:00 gmt+1100" moment('2015-12-12').tostring();  // return custom format, e.g. "2015-12-12" momentdate('2015-12-12').tostring(); 

i've been trying no success. i'm not sure if it's possible because of how moment written thought ask here.

my question answered here:

https://stackoverflow.com/a/34626333/2248573

note: solution works v2.11.0.

function extendedmoment() {    var self = moment();        self.__proto__ = extendedmoment.prototype;        return self;  }    extendedmoment.prototype.__proto__ = moment.prototype;    extendedmoment.prototype.tostring = function(){    return this.format('yyyy-mm-dd')  }    document.write("original: " + moment().tostring());  document.write("<br/>");  document.write("extended: " + extendedmoment().tostring());

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