How to check if a JavaScript array contains two specific values only

Question

I need to check if an array includes two values and only them.

This is my ugly solution for now:

if (myArray.includes('foo') && myArray.includes('bar') && myArray.length === 2) {
    // Do something
}

Update:

I may have to check three or more values as well. Any elegant solution? By the way, I'm using Lodash in this project.

score 12 · Accepted Answer · edited Jul 30 '18 at 18:09

12

I may have to check three or more values as well.

You could present your elements as an array, so if you've more than two items to check, the condition will still short and the same, using .every() method like:

myArray.every(elem => [1,2].indexOf(elem) > -1)

var myArray = [2, 1];
var myItems = [1, 2];

if (myArray.length === myItems.length && myArray.every(elem => myItems.indexOf(elem) > -1)) {
  console.log('PASS');
}

UPDATE:

Since you're using lodash, you could simply use _.difference() like:

if (_.size(myArray) === _.size(myItems) && _.difference(myArray, myItems).length === 0) {
    // Do something
}

edited Jul 30 '18 at 18:09

Peter Mortensen

30,738
21
105
131

answered Jul 30 '18 at 14:45

Zakaria Acharki

66,747
15
75
101

Check my lodash suggestion @isar – Zakaria Acharki Jul 30 '18 at 15:15
Thank you... I did but it didn't work as expected until I did this: `(myArray.length === myItems.length && _.difference(myArray, myItems).length === 0)`. – isar Jul 30 '18 at 15:36
Yes and if you want to use just lodash check my update using `_.size` – Zakaria Acharki Jul 30 '18 at 15:38
Why use a lodash function when vanilla JS is the better and clearer option? Does it offer any advantages? – vol7ron Jul 30 '18 at 17:28
Why you think it's _the better and clearer_? – Zakaria Acharki Jul 30 '18 at 17:30

Ankit Agarwal · Answer 2 · 2018-07-30T14:58:35.483

That is the proper way which you have used. But to improve the comparison you can put myArray.length === 2 at the begining as if the length is not 2 it will fail immediately:

if (myArray.length === 2 && myArray.includes('foo') && myArray.includes('bar')) {
  // do something
}

If your want to compare more values then you can check that with the help of a custom function:

function checkIncluded(myArray, checkingArray){
  if(myArray.length !== checkingArray.length){
    return false;
  }
  var match = true;
  for(var i=0; i<checkingArray.length; i++){
    if(!myArray.includes(checkingArray[i])){
      match = false;
      break;
    }
  }
  return match;
}


var neededItems = ['foo', 'bar', 'pat', 'jack'];
var myArray = ['jack', 'bar', 'foo', 'pat']
var included = checkIncluded(myArray, neededItems);
if (included) {
  console.log('All items matched');
} else {
  console.log('All items do not matched');
}

neededItems = ['bar', 'pat', 'jack'];
myArray = ['jack', 'bar', 'foo', 'pat']
included = checkIncluded(myArray, neededItems);
if (included) {
  console.log('All items matched');
} else {
  console.log('All items do not matched');
}

Returns true for `['foo', 'foo']` and `['foo', 'bar']` (but OP is not clear about it). — Salman A, Jul 30 '18 at 20:04

KooiInc · Answer 3 · 2018-07-31T05:03:06.100

A different and pretty simple approach:

const checkExact = (arr, v1, v2) => `${v1}${v2}` === String(arr.join(""));
const arr1 = [1, 2, 3];
const arr2 = [15, 23];
const arr3 = ["foo", "bar"];
const arr4 = ["foo", "bar", "foobar"];

console.log(
  checkExact(arr1, 1, 2),         // false
  checkExact(arr2, 15, 23),       // true
  checkExact(arr3, "foo", "bar"), // true
  checkExact(arr4, "foo", "bar")  // false
);

// more generic
const checkExactX = (arr, ...values) => 
  values.reduce( (p, n) => `${p}${n}`, "" ) === String(arr.join(""));
const arr5 = ["foo", "bar", "foobar", "barfoo"];
console.log(
  checkExactX(arr1, 1, 2),                   // false
  checkExactX(arr2, 15, 23),                 // true
  checkExactX(arr3, "foo", "bar"),           // true
  checkExactX(arr4, "foo", "bar", "foobar"), // true
  checkExactX(arr4, "foobarfoobar"),         // true
  checkExactX(arr5, "foo", "bar", "foobar")  // false
  
);

How to check if a JavaScript array contains two specific values only

3 Answers3