Function setProp

static/vuejs/vue.runtime.esm.js:5617–5626

(el, name, val)

var cssVarRE = /^--/;
var importantRE = /\s*!important$/;
var setProp = function (el, name, val) {
  /* istanbul ignore if */
  if (cssVarRE.test(name)) {
    el.style.setProperty(name, val);
  } else if (importantRE.test(val)) {
    el.style.setProperty(name, val.replace(importantRE, ''), 'important');
  } else {
    el.style[normalize(name)] = val;
  }
};

var prefixes = ['Webkit', 'Moz', 'ms'];