Function defineComputed

static/vuejs/vue.js:2791–2806

(target, key, userDef)

}

function defineComputed (target, key, userDef) {
  if (typeof userDef === 'function') {
    sharedPropertyDefinition.get = createComputedGetter(key);
    sharedPropertyDefinition.set = noop;
  } else {
    sharedPropertyDefinition.get = userDef.get
      ? userDef.cache !== false
        ? createComputedGetter(key)
        : userDef.get
      : noop;
    sharedPropertyDefinition.set = userDef.set
      ? userDef.set
      : noop;
  }
  Object.defineProperty(target, key, sharedPropertyDefinition);
}

function createComputedGetter (key) {
  return function computedGetter () {