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up vote 0 down vote favorite

Is there an easy way of knowing if and array contains all elements of another array?

Example:

var myarray = [1,2,3];
var searchinarray = [1,2,3,4,5];

searchinarray contains all elements of myarray, so this should return true.

Regards

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3 Answers 3

up vote 1 down vote accepted

A contains function should only visit members of the array to be contained that exist, e.g.

var myArray = [1,,2];
var searchInArray = [1,2,3];

contains(myArray, searchInArray);

should return true, however a simple looping solution will return false as myArray[1] doesn't exist so will return undefined, which is not present in the searchInArray. To easily avoid that and not use a hasOwnProperty test, you can use the Array every method:

function contains(searchIn, array) {
  return array.every(function(v){return this.indexOf(v) != -1}, searchIn);
}

so that:

var a = [1,,3];
var s = [1,2,3,4,5];

console.log(contains(s, a));  // true

You can add a contains method to all instances of Array if you wish:

if (typeof Array.prototype.contains == 'undefined') {
  Array.prototype.contains = function(a) {
    return a.every(function(v, i) {
      return this.indexOf(v) != -1;
    }, this);
  }
}

console.log(s.contains(a));      // true
console.log(s.contains([1,9]));  // false

You may need a polyfill for browsers that don't have .every (IE 8?).

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up vote 2 down vote

Here is an implementation of that function:

function contains(a, s) {
   for(var i = 0, l = s.length; i < l; i++) {
      if(!~a.indexOf(s[i])) {
         return false;
      }
   }
   return true;
}

This shows that it does what you describe:

> var myarray = [1,2,3];
> var searchinarray = [1,2,3,4,5];
> contains(myarray, searchinarray)
false
> contains(myarray, [1,2])
true
> contains(myarray, [2,3])
true
share|improve this answer
    
This should test that s[i] actually exists, or use a method like forEach that only visits members of s that exist. e.g. should contains(s, [,,1]) return true or false? –  RobG Oct 9 '14 at 6:12
up vote 0 down vote 
function compare(array, contains_array) {
 for(var i = 0; i < array.length; i++) {
  if(contains_array.indexOf(array[i]) == -1) return false;
 }
 return true;
}

compare(myarray, searchinarray);
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