Array contains all elements in other array

Question

Been trying to figure out how to do this for a while, but haven't had any success yet. If I have 2 arrays like this:

array1 = [
    { name: 'John', age : 25},
    { name: 'Jane', age : 58}
]
array2 = [
    { name: 'Jane', age : 58},
    { name: 'John', age : 25}
]

How can I chech if array1 contains all the elements of array2? Note - the ordering doesn't matter, I want to be able to write something like this:

if array1.containsAll array2
    console.log 'array1 contains all of the elements in array2'
else
    console.log 'array1 does not contain all of the elements in array2'

I've tried using the contains function, but I get an error like this:

Object .... has no method 'contains'

are you willing to consider a utility library, like underscore to get object comparison and composition? jsfiddle.net/no02qybh — Jed Schneider
– Jed Schneider, Commented Nov 12, 2014 at 3:13
There is no easy way to do this. alandarev's solution is close but you can't meaningfully compare the contents of objects using == (or ===) in JavaScript so you'd have to manually compare the values. You can hide some of the nastiness using a utility library (such as Underscore) but that's just shuffling the deck chairs around and hiding the complexity. — mu is too short
– mu is too short, Commented Nov 12, 2014 at 6:39

Billy Moon · Accepted Answer · 2014-11-11 15:30:21Z

1

I doubt this method has good performance, but it should be pretty robust, and is super simple to understand...

# sort function to marshall data into consistent format
sortfunc = (a,b)-> JSON.stringify(a) < JSON.stringify(b)

# if serialized, sorted arrays are equal, then all items are present
if JSON.stringify(array1.sort(sortfunc)) == JSON.stringify(array2.sort(sortfunc))
    console.log "same"
else
    console.log "different"

n.b. caveat is that order of object keys may or may not be significant, depending on whether JS engine respects object index order (JS spec states it is not required)

answered Nov 11, 2014 at 15:30

Billy Moon

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2 Comments

mu is too short Over a year ago

But there's no guarantee that { name: 'John', age : 25} will be '{"name":"John","age":25}' when JSONified rather than '{"age":25,"name":"John"}' and there's no guarantee that two JSON.stringify calls will put the keys in the same order. If you need the keys to be in a specific order (and you do), then you have to flatten them to arrays yourself.

mu is too short Over a year ago

Also, a sorting comparison function does not return a boolean value, it should return a positive, negative, or zero value to cover the three possibilities.

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