This function makes that an input field only allows numbers and just one comma, below you'll find the anonymous function version

onlyNumbersAndComma.js

//this is the functional version of the same code allowing you work with several inputs
var onlyNumbers = function(){
	'use strict';
	var coma = true,
	that = this;
	
	this.addEventListener('keyup', function(e){
		var key = e.keyCode,
		value = that.value;	
		if(key == 8 && value.search(/,/) === -1){
			coma = true;
		}
	});

	return function(e){
		var key = String.fromCharCode(e.keyCode),
		regex = /\d/;		
		if(!regex.test(key)){
			if(coma && key == ','){
				coma = false;
			}else{
				e.returnValue = false;
			}
		}
	};
};
//Now you can call onlyNumbers function in all your inputs
var text1 = document.getElementById('soloNum'),
text2 = document.getElementById('soloNum');

text1.addEventListener('keypress', onlyNumbers.call(text1));
text2.addEventListener('keypress', onlyNumbers.call(text2));

onlyNumbersAndCommaAnonymousFunction.js

//this is the anonymous function version
var soloNumTxt = document.getElementById('soloNum');

soloNumTxt.addEventListener('keypress', function(){
  'use strict';
	var coma = true;

	soloNumTxt.addEventListener('keyup', function(e){
		var key = e.keyCode,
		value = soloNumTxt.value;
		if(key == 8 && value.search(/,/) === -1){
			coma = true;
		}
	});

	return function(e){
		var key = String.fromCharCode(e.keyCode),
		regex = /\d/;		
		if(!regex.test(key)){
			if(coma && key == ','){
				coma = false;
			}else{
				e.returnValue = false;
			}
		}
	};
}());