Font size auto adjust to fit

Question

I\'m trying to do what the title says. I\'ve seen that font-size can be a percentage. So my guess was that font-size: 100%; would do it, but no.

Answer 1

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 = $("").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();
});