spatio(expression, unit = 'px', context = document.body)

// Measure 1em in pixels
spatio('10pt', 'px');  // 13.328125

// Calcucate at will!
spatio('calc(100vh - 5pt)'); // 957.328125, defaults to pixels

// Pass context element for relative space
var el = document.createElement('div');
el.style.fontSize = '24px';
document.body.appendChild(el);

spatio('1em', 'px', el); // 24

// Line height
spatio('1lh');

// Element width and height
spatio('100ew', document.body); // 1920
spatio('100eh', document.body); // 940

// Light seconds
spatio('0.00001ls', 'px') // 335.53125

// Add custom units

// A meter beer is defined as 13 beers, so 1 beer is 100cm / 13
spatio.addUnits({
  beer: spatio('calc(100cm / 13)')
});

spatio('1beer', 'cm') // 7.694789081885856