Using filter on an object

Question

I have an object that contains only simple key value pairs and I want to filter out any properties have falsey values. Is this possible using Array.prototype.filter()?

Answer 1

Is this possible using Array.prototype.filter()?

Yes, but not directly: You can do it after using Object.keys or similar:

var arrayOfTruthyValues = Object.keys(obj).filter(key => obj[key]);

The result is an array of truthy values.

If you want the end result to be an object, combining filter with reduce could do it:

var newObj = Object.keys(obj)
    .filter(key => obj[key])
    .reduce((newObj, key) => {
        newObj[key] = obj[key];
        return newObj;
     }, {});

That's mostly just using reduce as a looping construct (since we never actually change the accumulator value, we just keep returning the same object) which is sometimes considered an "abusage." :-) And it means we could do without the filter part and just put an if in the reduce, but...

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Note that Object.keys only includes an object's own, enumerable properties. If you want own properties even if they're not enumerable, that would probably be Object.getOwnPropertyNames instead.