Reduce Object items based on Array using underscore

Question

Having this:

array = []
array.push(111,2122,333,9)

obj.user = {
    '111'  : {},
    '2122' : {},
    '333'  : {},
    '44'   : {}
}

How can I get a new object containing only the elements that exist in the array?

In the case above, it would return:

{
    '111': {},
    '2122': {},
    '111': {}
}

I have tried this:

var newObj = _.keys(_.pick(obj.user, function(value, key) {
  if ( _.indexOf(array, parseInt(key)) != -1 ) {
    return obj.user[key]
  }
}));

Which works fine when testing on jsfiddle, but it crashes my app with process out of memory. The objects/arrays are not that large, maybe 20-30 items, but that piece of code gets executed quite a lot of times.

T.J. Crowder · Accepted Answer · 2018-10-07 13:37:33Z

4

You can use _.pick:

const result = _.pick(obj.user, array);

Live Example:

const array = [];
array.push(111,2122,333,9)

const obj = {
  user: {
    '111'  : {},
    '2122' : {},
    '333'  : {},
    '44'   : {}
  }
};

const result = _.pick(obj.user, array);

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.9.1/underscore-min.js"></script>

edited Oct 7, 2018 at 13:37

T.J. Crowder

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answered Oct 7, 2018 at 13:34

Ozzy Walsh

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2 Comments

T.J. Crowder Over a year ago

Recommend avoiding "Try this:" followed by code. Say what you've used, and ideally when it's something like _.pick, link to it (see my edit).

rlcabral Over a year ago

Running with this code for 15 minutes and so far the app didn't crash. Thanks.

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