can/bower_components/modernizr/feature-detects/css-calc.js

MIT-licensed, client-side, JavaScript framework that makes building rich web applications easy.

// Method of allowing calculated values for length units, i.e. width: calc(100%-3em) http://caniuse.com/#search=calc
// By @calvein

Modernizr.addTest('csscalc', function() {
    var prop = 'width:';
    var value = 'calc(10px);';
    var el = document.createElement('div');

    el.style.cssText = prop + Modernizr._prefixes.join(value + prop);

    return !!el.style.length;
});