Font scaling based on width of container

Question

I\'m having a hard time getting my head around font scaling.

I currently have a website with a body font-size of 100%. 100% of what though? This seems t

Answer 1

Using vw, em & co. works for sure, but IMO it always needs a human's touch for fine-tuning.

Here's a script I just wrote based on @tnt-rox' answer that tries to automatize that human's touch:

$('#controller').click(function(){
    $('h2').each(function(){
        var
            $el = $(this),
            max = $el.get(0),
            el = null
        ;
        max =
            max
            ? max.offsetWidth
            : 320
        ;
        $el.css({
            'font-size': '1em',
            'display': 'inline',
        });
        el = $el.get(0);

        el.get_float = function(){
            var
                fs = 0
            ;
            if (this.style && this.style.fontSize) {
                fs = parseFloat(this.style.fontSize.replace(/([\d\.]+)em/g, '$1'));
            }
            return fs;
        };

        el.bigger = function(){
            this.style.fontSize = (this.get_float() + 0.1) + 'em';
        };

        while (el.offsetWidth < max) {
            el.bigger();
        }

        // Finishing touch.
        $el.css({
            'font-size': ((el.get_float() -0.1) +'em'),
            'line-height': 'normal',
            'display': '',
        });
    });  // end of (each)
});    // end of (font scaling test)

div {
  width: 50%;
  background-color: tomato;
  font-family: 'Arial';
}

h2 {
  white-space: nowrap;
}

h2:nth-child(2) {
  font-style: italic;
}

  
Lorem ipsum dolor
  
Test String
  
Sweet Concatenation
  
Font Scaling

It basically reduces the font-size to 1em and then starts incrementing by 0.1 until it reaches maximum width.

JSFiddle