code: function unitProperty (property, value) {
    if (value !== +value) {
      return value
    }
  
    if (unitCache[property]) {
      return value + unitCache[property]
    }
  
    supportElement.style[property] = 0
  
    let propValue = supportElement.style[property]
    let match = propValue.match && propValue.match(UNIT_REG)
  
    if (match) {
      return value + (unitCache[property] = match[1])
    }
  
    return value
  }
docs: Obtain the unit of a property and add it to the value has no unit if exists.
  
  @param {string} property property
  @param {(string|number)} value A value maybe needs unit.
  @return {(string|number)}