How to: Reduce font-size if a line breaks

Question

I have a span inside of a div and the div must remain 200px wide and the text must fit on one line within the div. The text within the span is dynamically generated so I can't possibly know which content will break to a new line and which will not.

<div style="width:200px">
  <span style="font-size:12px;">This sentence is too large to fit within the div.</span>
</div>

If I use the CSS property white-space:nowrap; the words will spill to the outside of the div, which of course, we don't want.

How would I reduce the font-size (or zoom) based on if the line breaks or not? I would prefer a CSS answer, but I understand if that is outside of CSS's abilities.

Answer 1

One fairly nasty way: loop decreasing the overflowing span until its less that the div width;

var divWidth = $("#theDiv").width();
var text = $("#text");
var fontSize = 12;

while (text.width() > divWidth)
  text.css("font-size", fontSize -= 0.5);

text.css("display", "inline");

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<div id="theDiv" style="width:200px; border:1px solid red;">
  <span id="text" style="display:none;white-space:nowrap;">This sentence is too large to fit within the div.</span>
</div>