拼接内部 Object.keys(obj).forEach(function(index)

Question

Is it ok to do something like this in node.js:

Object.keys(obj).forEach(function(index) { 
   if (index == 'sth')
      obj.splice(obj.indexOf(index), 1);
}

I wonder if this splice will do the expected thing if the script is executed by many clients writing in/out into the obj object.

Answer 1

obj is indeed an object and index can be an alphanumeric value. So, splice does not work in objects, instead should use delete. Same question then,is it ok to use delete inside a foreach of an object?

You're not doing forEach on obj . (You can't, forEach is only defined for array-like things.) You're doing forEach on an array created by finding all of the own enumerable properties of obj via Object.keys .

Let's look at the code with the change you describe above and the syntax error corrected:

Object.keys(obj).forEach(function(key) { 
   if (key == 'sth')
      delete obj[key];
});

Sure, you can delete properties from obj within the forEach callback on the array from Object.keys . It has no effect at all on the array that you're looping over.

---

Side note: When you use delete on an object, on V8 (the JavaScript engine NodeJS uses) and some others it markedly reduces the performance of looking up properties of that object later, because it goes from the optimized version to a "dictionary mode" version. Of course, this only matters if you've identified the object as the source of a performance problem; until then, delete away... :-)