_.isEmpty Behavior on numbers

[siyegen]

var cow = {a: 1, b: {}, c: []};
_.isEmpty(cow); // returns false

isEmpty works fine on objects containing numbers as the only 'non-empty' values

_.isEmpty(cow.a); // returns true

However the individual k,v of a:1 is considered empty.

I did read through the issues and noted that originally _.isEmpty wasn't intended for strings, so this might be intended. If it's not intended then I have a branch I can make a pull request for.

[siyegen]

The use case I ran into this was doing something like this

_.each(cow, function(v, k) {
  if (_.isEmpty(v)) {
    // do something with k because of v being empty
  }
});

So cow.a would be treated just like cow.b and cow.c. I can code around it, but thought it would be so much neater if I didn't have to (and if it didn't break the spirit or vision of underscore)

[jashkenas]

Yep, _.isEmpty is only defined for objects an arrays. You shouldn't use it on strings or numbers.

[michaelficarra]

You shouldn't use it on numbers. Strings are okay:

79f65b4
https://github.com/documentcloud/underscore/blob/322a64135dc3c4a649f102e962054310c2b39c04/underscore.js#L808

[josser]

So, what alternatives we have to use on numbers?

[morficus]

@jashkenas or @michaelficarra: any particular reason why _.isNumber is not called with in _.isEmpty? (same way _.isArray and _.isString are being used)

[michaelficarra]

Any reason why it should?

[morficus]

Well, yes. I'm glad you asked :-)

They way I have seen most folks use _.isEmpty is pretty much to check if a value (any value) has been assigned to a particular variable. I have seen many developers run in to issues because of this.

Even the official documentation states "Returns true if object contains no values" - and a number should qualify as a value.

If there I some type of larger implication in making this change that my I just can't see, then my 2nd-best suggestion would be to please update the documentation to clearly state that it should not be used for numbers :-)

[jashkenas]

Why would you ever want to pass a number into isEmpty, instead of just checking if the number is null?

Even the official documentation states "Returns true if object contains no values"

Quite right. In JavaScript, a number is (very sadly) not an object.

[jdalton]

I think this could be cleared up with _.isEmpty doc tweaks. What devs are looking for is _.exists.

[melnikov-s]

It makes sense for _.isEmpty(a) to mean "is a an empty object?", kind of like if the statement : if obj == {} worked on values and not on references. Therefore values like numbers would return false and so would null and undefined.

an example implementation of _.isEmpty might be:

_.isEmpty = function(a) {
  return _.isEqual(a, {}) || _.isEqual(a, []) || _.isEqual(a, '');
}

[josser]

@jashkenas That's probably because in some other languages "empty" determines whether variable is empty or not :) http://www.php.net/manual/en/function.empty.php

[morficus]

+1 to @josser - mostly because I have a PHP background :-p
But I think just clarifying it in the documentation could also be enough. I seriously see folks run into this every other week.

[timurridjanovic]

I ran into this today.. I was using it with _.omit

_.omit(someObject, _.isEmpty);

[panialex]

the real use of isEmpty should be if the value is empty, the value that you don't know what it is, or wherever value that you need to know what it is, but js its a pile of bugs so I understand why it just generates more bugs