gist.js

function inputCheck (shitumon, outputNum) {

		var condition = true;
		var a = -1;
		while(condition) {
			console.log(a);
			if (isNaN(a) || a <= -1) {
				console.log("Invalid imput, please enter a number only!<br>");
				a = 5;
			} else {
				condition = false;
				outputNum = a;
			}
		}
		return outputNum;
	}
	
	inputCheck("Please enter a number!", table);