vue底层

defineReactive-用于定义非data变量响应

  function defineReactive$$1 (
    obj,
    key,
    val,
    customSetter,
    shallow
  ) {
    
    
    var dep = new Dep();

    var property = Object.getOwnPropertyDescriptor(obj, key);
    if (property && property.configurable === false) {
    
    
      return
    }

    // cater for pre-defined getter/setters
    var getter = property && property.get;
    var setter = property && property.set;
    if ((!getter || setter) && arguments.length === 2) {
    
    
      val = obj[key];
    }

    var childOb = !shallow && observe(val);
    Object.defineProperty(obj, key, {
    
    
      enumerable: true,
      configurable: true,
      get: function reactiveGetter () {
    
    
        var value = getter ? getter.call(obj) : val;
        if (Dep.target) {
    
    
          dep.depend();
          if (childOb) {
    
    
            childOb.dep.depend();
            if (Array.isArray(value)) {
    
    
              dependArray(value);
            }
          }
        }
        return value
      },
      set: function reactiveSetter (newVal) {
    
    
        var value = getter ? getter.call(obj) : val;
        /* eslint-disable no-self-compare */
        if (newVal === value || (newVal !== newVal && value !== value)) {
    
    
          return
        }
        /* eslint-enable no-self-compare */
        if (customSetter) {
    
    
          customSetter();
        }
        // #7981: for accessor properties without setter
        if (getter && !setter) {
    
     return }
        if (setter) {
    
    
          setter.call(obj, newVal);
        } else {
    
    
          val = newVal;
        }
        childOb = !shallow && observe(newVal);
        dep.notify();
      }
    });
  }