将 JavaScript 对象转换为 ClojureScript:getter 和 setter properites

Question

我正在努力解决以下问题：

通常JS对象通过js->clj转换为ClojureScript。这适用于原型对象的对象。对于我正在使用的另一个：

(defn jsx->clj [o]
  (reduce (fn [m v] (assoc m (keyword v) (aget o v)))  {} (.keys js/Object o)))

我发现，作为幕后获取函数的"属性"不能通过这些操作进行转换。

有人对此有任何经验吗？

Answer 1

我不确定你说"幕后的 getter 函数不能通过这些操作转换"是什么意思。

其中一个问题是，当你像这样将JS对象转换为CLJS映射时，getter和setters将不会绑定到原始JS对象，因此它们将无法访问该对象的属性。

请考虑以下代码：

;; This is your function, no changes here.
(defn jsx->clj [o]
  (reduce (fn [m v] (assoc m (keyword v) (aget o v)))  {} (.keys js/Object o)))

;; This is an improved version that would handle JS functions that
;; are properties of 'o' in a specific way - by binding them to the
;; 'o' before assoc'ing to the result map.
(defn jsx->clj2 [o]
  (reduce (fn [m v]
            (let [val (aget o v)]
              (if (= "function" (goog/typeOf val))
                (assoc m (keyword v) (.bind val o))
                (assoc m (keyword v) val))))
          {} (.keys js/Object o)))
;; We create two JS objects, identical but distinct. Then we convert
;; both to CLJS, once using your function, and once using the improved
;; one.
;; Then we print results of accessing getter using different methods.
(let [construct-js (fn [] (js* "new (function() { var privProp = 5; this.pubProp = 9; this.getter = function(x) { return privProp + this.pubProp + x; }; })"))
      js-1 (construct-js)
      js-2 (construct-js)
      clj-1 (jsx->clj js-1)
      clj-2 (jsx->clj2 js-2)]
  (.log js/console "CLJS objects: " (.getter js-1 10) ((:getter clj-1) 10) (.getter js-2 10) ((:getter clj-2) 10)))

这将打印：

CLJS objects:  24 NaN 24 24

这意味着以下代码：((:getter clj-1) 10)失败，而((:getter clj-2) 10)按预期工作。第二个有效，因为 .bind（） 已被用于将函数与 JS 对象正确绑定。

这个问题，如果这确实是你失败的原因，相当于JS中有时会犯的以下错误：

var Constructor = function() {
  var privProp = 5;
  this.pubProp = 9;
  this.getter = function(x) {
    return privProp + this.pubProp + x;
  };
}
var obj1 = new Constructor();
var obj2 = new Constructor();
var fn1 = obj1.getter;             // Invalid, fn1 will not be bound to obj1.
var fn2 = obj2.getter.bind(obj2);  // Note .bind here.
console.log(fn1(10), fn2(10));

这将打印类似的输出：

NaN 24

同样，尚未绑定fn1 obj1返回无效输出。