Js error on android 5.1 and lower

ionic-v1
1

Hello guyz my ionic app is wroking very well in android 6 and above but while testing it in android 5.1 and lower
it gives out error:

TypeError: undefined is not a function
    at Array.findBy (file:///android_asset/www/js/app.js:35:17)
    at Object.$scope.vEvents.initApp (file:///android_asset/www/js/controllers/languagesCtrl.js:20:51)
    at fn (eval at <anonymous> (file:///android_asset/www/lib/ionic/js/ionic.bundle.js:27643:15), <anonymous>:4:249)
    at file:///android_asset/www/lib/ionic/js/ionic.bundle.js:65429:9
    at Scope.$eval (file:///android_asset/www/lib/ionic/js/ionic.bundle.js:30400:28)
    at Scope.$apply (file:///android_asset/www/lib/ionic/js/ionic.bundle.js:30500:25)
    at HTMLAnchorElement.<anonymous> (file:///android_asset/www/lib/ionic/js/ionic.bundle.js:65428:13)
    at defaultHandlerWrapper (file:///android_asset/www/lib/ionic/js/ionic.bundle.js:16792:11)
    at HTMLAnchorElement.eventHandler (file:///android_asset/www/lib/ionic/js/ionic.bundle.js:16780:9)
    at triggerMouseEvent (file:///android_asset/www/lib/ionic/js/ionic.bundle.js:2953:7)

I am defining array findby method which works well in android 6 and above

Array.prototype.findBy = function(key, value) {
		function iter(item) {
			if(item[key] === value) {
				return true;
			}
			return false;
		}

		return this.find(iter);
	};

It looks like ionic is unable to read the find() method

2

Is find available in Android 5.1 and below?
Often it is not the Android version that is responsible, but the version of the Webview active on the device.