As a programmer, often you need to either know the size of the user’s screen (basically their resolution); or the more important available space inside their browser where you can display your content. You avoid less clipping and display issues if you can distinguish the two.

function getWidth(){
	if(document.all){
        	return document.body.clientWidth;
	}else{
        	return innerWidth;
	}
};

function getHeight(){
	if(document.all){
        	return document.body.clientHeight;
    	}else{
        	return innerHeight;
    	}
};
document.writeln("Screen Size : " + screen.width + " x " + screen.height + " (Includes Everything on Screen)<br/>");
document.writeln("Width: " + getWidth() + " x  Height: " + getHeight() + " (What's Available INSIDE the Browser)");

DEMO | DOWNLOAD

String manipulation is one of the most basic things you need to know.

	<form id="reverse" action="javascript:doIT()">
		<table>
			<th colspan="2">Reverse String</th>
			<tr>
				<td><input type="text" id="string" placeholder="enter a string" required /></td>
			</tr>
			<tr>
				<td class="button"><input type="submit" id="reverse" value="Reverse" /></td>
			</tr>
			<tr>
				<td><strong>LOG :</strong><br/><div id="log"></div></td>
			</tr>
		</table>
	</form>
	<script>
		function doIT(){
			var string = document.getElementById("string");
			var log = document.getElementById("log");
			log.innerHTML += "&emsp;" + string.value + " = " + reversal(string.value) + "<br/>";
			string.value = reversal(string.value);
		}
		function reversal(s) {
			var r = s.split("").reverse().join("");
			return r;
		}
	</script>

DEMO | DOWNLOAD