Detonify a string in Javascript

detonify.js

String.prototype.detonify = function () {
	'use strict';
  // set string of characters with tones
	let tones = 'ΆάΈέΉήΌόΎύΏώΊΪϊίΫϋ'.split('')
  // set the equivalent string of characters without tones
	let detones = 'ΑαΕεΗηΟοΥυΩωΙΙιιΥυ'.split('')
	let str = this.toString()
	for (let key in tones) {
		let regex = new RegExp(tones[key], 'g')
		str = str.replace(regex, detones[key] || tones[key])
	}
	return str;
}