Limit the range of a numeric textbox with Jquery

textbox-range-limit.js

jQuery("#textbox_id").on("keypress", function(e){
		var currentChar = parseInt(String.fromCharCode(e.keyCode), 10);
		    if(!isNaN(currentChar)){
		        var nextValue = elem.val() + currentChar; //It's a string concatenation, not an addition
		        
		        if(parseInt(nextValue, 10) <= 20) return true;
		    }
		    
		    return false;
		});