Expected identifier instead and instead saw 'let' : I am trying filter the object and when I do it I am getting this error what actually it is saying I am not getting it.

> Expected identifier instead and instead saw 'let'.

This is my filter function

	var arr = $scope.items; //onject data
	var stringToFilter = newSortingOrder.toString();
	let obj = arr.find(o => o.id === stringToFilter); //error stopping in this line.