javascript - 当 obj 中的键被转换为 __indexOf 与 Coffeescript 的用法时

Question

这一茶匙咖啡......

    _pickInConf = (sourceConf,propsToPick...) ->
      newConfWithPickedProperties = {}
      newConfWithPickedProperties[key] = sourceConf[key] for key in Array::.concat.apply Array::,propsToPick when key in sourceConf
      newConfWithPickedProperties

... 被编译成:

_pickInConf = function() {
  var key, newConfWithPickedProperties, propsToPick, sourceConf, _i, _len, _ref;
  sourceConf = arguments[0], propsToPick = 2 <= arguments.length ? __slice.call(arguments, 1) : [];
  newConfWithPickedProperties = {};
  _ref = Array.prototype.concat.apply(Array.prototype, propsToPick);
  for (_i = 0, _len = _ref.length; _i < _len; _i++) {
    key = _ref[_i];
    if (__indexOf.call(sourceConf, key) >= 0) {
      newConfWithPickedProperties[key] = sourceConf[key];
    }
  }
  return newConfWithPickedProperties;
};

...并利用:

__indexOf = [].indexOf || function(item) { for (var i = 0, l = this.length; i < l; i++) { if (i in this && this[i] === item) return i; } return -1; };

我希望 Coffeescript 编译器能够转译这个 block :

when key in sourceConf

进入:

if (key in sourceConf) {

...这就是我要用 JS 编写代码的意思...

有没有办法强制 Coffescript 输出这种 JS？或者让它理解 sourceConf 是一个对象，而不是一个数组？

预先感谢您的回答!

Answer 1

您希望 of 而不是 in 来迭代对象的键:http://coffeescript.org/#loops (接近本节末尾)

对此进行扩展:

for a in items when a of obj
  stuff

编译为

var a, _i, _len;

for (_i = 0, _len = items.length; _i < _len; _i++) {
  a = items[_i];
  if (a in obj) {
    stuff;

  }
}

它正在使用你正在寻找的 a in obj