Compare an array with keys to keys in an object JavaScript

Question

I have an array with keys like ["1", "5", "9"] And I have an object with the same keys, something like this: selections: { "5": {}, "12": {} }

What is the easiest way to get a boolean value out of it. It should return true if any of the keys in the array is present in my object. I am using angular and lodash, is there any smart solution for this or do I need to do a loop for it? And if I do a loop, what is the most efficient way?

I tried _.every(["1", "2", "5"], function (id) { if (!_.includes(_.pluck(selections, "id"), id)) { return true; } }); — dom
– dom, Commented Oct 25, 2015 at 17:40

Pavel Komiagin · Accepted Answer · 2015-10-25 17:35:52Z

3

Did you try to use hasOwnProperty()?

function check() {
  var selections = { "5": {}, "12": {} };
  return ["1", "5", "9"].filter(function(value) {
    return selections.hasOwnProperty(value);
  }).length > 0;
}

answered Oct 25, 2015 at 17:35

Pavel Komiagin

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5 Comments

An0nC0d3r Over a year ago

Nice and tidy, like it! +1

clocksmith Over a year ago

The problem with this is that it goes through the entire array all of the time. You can stop as soon as you find one match.

Etse Over a year ago

what about using array.some rather than filter? No need for the length-check then.

Pavel Komiagin Over a year ago

Totally agree, this solution not efficient on large inputs

user5004821 Over a year ago

@Etse the issue with every is that it only returns true if all values in the array pass the predicate - whereas op wants it to return true if any value matches the predicate - so array.some is a better option in this case (and returns immediately if predicate returns true as opposed to going through entire array).

user5004821 · Accepted Answer · 2015-10-25 17:39:52Z

3

var selections = { "5": {}, "12": {} };
var array = ["1", "5", "9"];

array.some(key => selections.hasOwnProperty(key));

answered Oct 25, 2015 at 17:39

user5004821

1 Comment

Stephen Quan Over a year ago

Nice use of Arrow functions but it does require ECMAScript 2015 which, for some, may not yet be available on their platform.

Nina Scholz · Accepted Answer · 2015-10-25 18:42:17Z

1

Just a single line of code:

var array = ["1", "5", "9"],
    obj = { "5": {}, "12": {} },
    any = array.some(function (a) { return a in obj; });
document.write(any);

edited Oct 25, 2015 at 18:42

answered Oct 25, 2015 at 18:09

Nina Scholz

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1 Comment

dom Over a year ago

this is a nice solution, however it only works if all my keys matches the keys in the object. But seems your solution also works with array.some for any key, so that would be it :)

clocksmith · Accepted Answer · 2015-10-25 17:43:53Z

0

var keys = ["1", "5", "9"]; 
var selections = {"5": {}, "12": {}};   

function hasAnyKey(keys, selections) {
  for (var i = 0; i < keys.length; i++) {
    if (selections[keys[i]]) {
      return true;
    }
  }
  return false;
};

hasAnyKey(keys, selections);

This solution will return as soon as there is 1 match, which equates to returning true when there is at least 1 match, which is what you want. In theory, this will work faster than the solutions with Array.prototype.filter for larger inputs.

edited Oct 25, 2015 at 17:43

answered Oct 25, 2015 at 17:37

clocksmith

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Comments

Stephen Quan · Accepted Answer · 2015-10-25 18:49:30Z

0

Array.prototype.some() executes the callback function once for each element present in the array until it finds one where callback returns a true value. If such an element is found, some() immediately returns true. Otherwise, some() returns false. Array.prototype.some() is in ECMAScript 1.5 and should work just about anywhere.

function compareArrayToObject(array, obj) {
    return array.some(function (a) { return a in obj; });
}
var array = ["1", "5", "9"];
var obj = { "5": {}, "12": {} };
var result = compareArrayToObject(array, obj);
document.write(result);

edited Oct 25, 2015 at 18:49

answered Oct 25, 2015 at 18:26

Stephen Quan

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