I was wondering if we can build a zone abbreviations in plain javascript?

I landed in bellow small snippet,

Date.prototype.zoneAbbr = function(){
    return (((new Date()).toString().split(/[()]/)[1]).match(/[A-Z]/g) || []).join('')
}

(new Date()).zoneAbbr(); // output - IST

I want to hear if we have better alternative for this? Is there any improvements i can make to this polyfill?