ParseInt

by Anton Bagayev

JavaScript

function parseInt (input) {
	let result = 0;
	
	for (let i = 0; i < input.length; i++) {
		result *= 10;
		let asciiValue = input.charCodeAt(i);
		if ((asciiValue >= 48) && (asciiValue <= 57)) {
			result += asciiValue - 48;
		} else {
			alert("Not an integer!");
			return;
		}
	}
	
	alert(result);
}

parseInt("10245678899");