I was looking into this for work and I liked tnt-rox's answer, but I couldn't help but notice that it had some extra overhead that could be cut out.
document.body.setScaledFont = function(){
this.style.fontSize = (this.offsetWidth*0.35)+'%';
return this;
}
document.body.setScaledFont();
Cutting out the overhead makes it run a little bit quicker if you add it to an onresize event.
If you are only looking to have the font inside a specific element set to resize to fit, you could also do something like the following
window.onload = function(){
var scaledFont = function(el){
if(el.style !== undefined){
el.style.fontSize = (el.offsetWidth*0.35)+'%';
}
return el;
}
navs = document.querySelectorAll('.container>nav'),
i;
window.onresize = function(){
for(i in navs){
scaledFont(navs[i]);
}
};
window.onresize();
};
I just noticed nicolaas' answer also had some extra overhead. I've cleaned it up a bit. From a performance perspective, I'm not really a fan of using a while loop and slowly moving down the size until you find one that fits.
function setPageHeaderFontSize(selector) {
var $ = jQuery;
$(selector).each(function(i, el) {
var text = $(el).text();
if(text.length) {
var span = $("<span>").css({
visibility: 'hidden',
width: '100%',
position: 'absolute',
'line-height': '300px',
top: 0,
left: 0,
overflow: 'visible',
display: 'table-cell'
}).text(text),
height = 301,
fontSize = 200;
$(el).append(span);
while(height > 300 && fontSize > 10) {
height = span.css("font-size", fontSize).height();
fontSize--;
}
span.remove();
$(el).css("font-size", fontSize+"px");
}
});
}
setPageHeaderFontSize("#MyDiv");
And here is an example of my earlier code using jquery.
$(function(){
var scaledFont = function(el){
if(el.style !== undefined){
el.style.fontSize = (el.offsetWidth*0.35)+'%';
}
return el;
};
$(window).resize(function(){
$('.container>nav').each(scaledFont);
}).resize();
});