How do I access the Object.prototype method in the following logic?

问题

I am using the following logic to get the i18n string of the given key.

export function i18n(key) {
  if (entries.hasOwnProperty(key)) {
    return entries[key];
  } else if (typeof (Canadarm) !== 'undefined') {
    try {
      throw Error();
    } catch (e) {
      Canadarm.error(entries['dataBuildI18nString'] + key, e);
    }
  }
  return entries[key];
}

I am using ESLint in my project. I am getting the following error:

Do not access Object.prototype method 'hasOwnProperty' from target object. It is a 'no-prototype-builtins' error.

How do I change my code to resolve this error ? I don't want to disable this rule.

回答1:

You can access it via Object.prototype:

Object.prototype.hasOwnProperty.call(obj, prop);

That should be safer, because

Not all objects inherit from Object.prototype
Even for objects which inherit from Object.prototype, the hasOwnProperty method could be shadowed by something else.

Of course, the code above assumes that

The global Object has not been shadowed or redefined
The native Object.prototype.hasOwnProperty has not been redefined
No call own property has been added to Object.prototype.hasOwnProperty
The native Function.prototype.call has not been redefined

If any of these does not hold, attempting to code in a safer way, you could have broken your code!

Another approach which does not need call would be

!!Object.getOwnPropertyDescriptor(obj, prop);

回答2:

It seems like this would also work:

key in entries

since that will return a boolean on whether or not the key exists inside the object?

回答3:

For your specific case, the following examples shall work:

if(Object.prototype.hasOwnProperty.call(entries, "key")) {
    //rest of the code
}

if(Object.prototype.isPrototypeOf.call(entries, key)) {
    //rest of the code
}

if({}.propertyIsEnumerable.call(entries, "key")) {
    //rest of the code
}

回答4:

I hope I won't get downvoted for this, probably will, but !

var a = {b: "I'm here"}
if (a["b"]) { console.log(a["b"]) }
if (a["c"]) { console.log("Never going to happen") }

Has, insofar, never broken my code 😬 But I'm not sure if it is the case in all web browsers...

(Also, if Canadarm is undefined, your code seem to return entries[key]; even if key is not in entries...)

来源：https://stackoverflow.com/questions/39282873/how-do-i-access-the-object-prototype-method-in-the-following-logic

标签

javascript

ecmascript-6

eslint