number(tweenProp) {
    if (tweenProp in this.valuesEnd && !KEC[tweenProp]) { // numbers can be 0
      KEC[tweenProp] = (elem, a, b, v) => {
        /* eslint-disable */
        elem.innerHTML = numbers(a, b, v) >> 0;
        /* eslint-enable */
      };
    }
  }
onStartWrite.number

Sets the property update function.
@param {string} tweenProp the property name