$(function() {
	const isNumericInput = (event) => {
		const key = event.keyCode;
		return ((key >= 48 && key <= 57) || // Allow number line
			(key >= 96 && key <= 105) // Allow number pad
		);
	};

	const isModifierKey = (event) => {
		const key = event.keyCode;
		return (event.shiftKey === true || key === 35 || key === 36) || // Allow Shift, Home, End
			(key === 8 || key === 9 || key === 13 || key === 46) || // Allow Backspace, Tab, Enter, Delete
			(key > 36 && key < 41) || // Allow left, up, right, down
			(
				// Allow Ctrl/Command + A,C,V,X,Z
				(event.ctrlKey === true || event.metaKey === true) &&
				(key === 65 || key === 67 || key === 86 || key === 88 || key === 90)
			)
	};

	const enforceFormat = (event) => {
		// Input must be of a valid number format or a modifier key, and not longer than ten digits
		if(!isNumericInput(event) && !isModifierKey(event)){
			event.preventDefault();
		}
	};

	const formatToPhone = (event) => {
		if(isModifierKey(event)) {return;}

		const target = event.target;
		const input = event.target.value.replace(/\D/g,'').substring(0,10); // First ten digits of input only
		const areaCode = input.substring(0,3);
		const middle = input.substring(3,6);
		const last = input.substring(6,10);

		if(input.length > 6){target.value = `${areaCode}-${middle}-${last}`;}
		else if(input.length > 3){target.value = `${areaCode}-${middle}`;}
		else if(input.length > 0){target.value = `${areaCode}`;}
	};

	let inputElements = document.querySelectorAll('.phone-number-formatting');

	inputElements.forEach((item) => {
		item.addEventListener('keydown',enforceFormat);
		item.addEventListener('keyup',formatToPhone);
	});
});