The Poor Man's FitText

pmft.js

/* Requires jQuery
** Include this file or copy/paste into your document.
** Call the function, passing the selector as a jQuery-style string.
** Offset is a number used to keep the text just short of the width of the parent to avoid rounding errors that will wrap the text. 
** You can use the offset to adjust how close you want the width to be. Offset is optional and defaults to 10.
** Step defines the increase in font size. If you find one or more of your elements pushes out further than the others, adjust this 
** number.
** For this to work, the element containing the text must be set to display:inline or inline-block, and the parent should be anything
** other than inline. So, if you have an h1 inside a header, you will need to make sure the h1 is inline or inline-block and the header
** isn't inline.
*/

function pmft(selector, offset, step){
	if(offset == null){
		offset = 10;
	}
	if(step == null){
		step = 1;
	}
	
	var containerWidth = $(selector).parent().outerWidth(true),
	thisWidth = $(selector).outerWidth(true) + offset,
	thisFontSize = parseFloat($(selector).css('font-size'));
	
	if($(selector).length && thisWidth != NaN && containerWidth != NaN){
		
		if(thisWidth < containerWidth){
			
			while(thisWidth < containerWidth){
				thisFontSize += step;
				$(selector).css('font-size', thisFontSize + 'px');
				thisWidth = $(selector).outerWidth(true) + offset;
			}
			
		} else if (thisWidth > containerWidth){
		    
			while(thisWidth > containerWidth){
				thisFontSize -= step;
				$(selector).css('font-size', thisFontSize + 'px');
				thisWidth = $(selector).outerWidth(true) + offset;
			}
			
		} else {
		    
			return false;
			
		}
	}
}