JSFiddle - React, Tailwind, and code Playground

HTML

<pre id="out">
perspective property parsing:
</pre>

JavaScript

var style = document.createElement('div').style;
var tests = {
  '10px': true,
  '0px': false,
  '-10px': false,
  'calc(10px)': true,
  'calc(0px)': true,
  'calc(-10px)': true,
  'calc(10em - 10px)': true,
};
var valid = {true: 'valid', false: 'invalid'};
Object.keys(tests).forEach(function(value) {
  style.perspective = '';
  style.perspective = value;
  var actual = style.perspective != '';
  var expected = tests[value];
  var pass = actual == expected;
  out.textContent += pass ? 'pass' : 'FAIL';
  out.textContent += ': ' + value + ' is ' + valid[actual];
  if (!pass)
    out.textContent += ' (should be ' + valid[expected] + ')';
  out.textContent += '\n';
});