Determining whether one array contains the contents of another array in JavaScript/CoffeeScript

Question

In JavaScript, how do I test that one array has the elements of another array?

arr1 = [1, 2, 3, 4, 5] [8, 1, 10, 2, 3, 4, 5, 9].function_name(arr1) # => true 

Answer 1

No set function does this, but you can simply do an ad-hoc array intersection and check the length.

[8, 1, 10, 2, 3, 4, 5, 9].filter(function (elem) {     return arr1.indexOf(elem) > -1; }).length == arr1.length 

A more efficient way to do this would be to use .every which will short circuit in falsy cases.

arr1.every(elem => arr2.indexOf(elem) > -1); 

Answer 2

You can use array.indexOf():

pseudocode:

function arrayContainsAnotherArray(needle, haystack){   for(var i = 0; i < needle.length; i++){     if(haystack.indexOf(needle[i]) === -1)        return false;   }   return true; }