compare two arrays if keys match with underscore.js

Question

I have an array with permissions from Facebook and an array of the permissions that the user shouldve given:

window.FB.api('/me/permissions', function(perm){                     
    if(perm){
       var given_permissions =  _.keys(perm['data'][0];
       var needed_permissions = ["publish_stream", "email"];
       //now check if given permissions contains needed permissions
    }
}

Now I want to compare if all the needed_permissions are in given_permissions, in an underscore savvy way (without looping two arrays myself and compare values). I saw a _.include method, but this compares an array with a value. I want to return true if all the permissions are available and else a false. I was looking for a nice single line call if possible.

The reason for this is, that FB.login returns true even if the user chooses to cancel the extended permissions. So I need to doublecheck this.

mu is too short · Accepted Answer · 2012-08-01 08:38:38Z

18

You could use _.difference to see if removing the given permissions from your required permissions leaves anything behind:

var diff = _(needed_permissions).difference(given_permissions)
if(diff.length > 0)
    // Some permissions were not granted

A nice side effect of this is that you get the missing permissions in diff in case you want to tell them what's wrong.

answered Aug 1, 2012 at 8:38

mu is too short

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2 Comments

Jareish Over a year ago

That's also a nice solution. I'll have to mark the other one as answer, because that's basicly what I asked for, but I think I'll use this solution so I can provide better feedback.

user2493235 Over a year ago

I disagree and think it would be much more useful to make this your accepted answer. _.difference is exactly what you asked for ("compare two arrays if keys match with underscore.js" - the rest was really speculation I think) and indeed the answer you "accepted" because you used it! Just a thought to help others looking at this. I guess not everyone will check past the accepted answer. The accepted answer is pretty poor as a solution since it adds nothing when underscore provides a function to do exactly that "out of the box".

xiaowl · Accepted Answer · 2012-08-01 08:28:12Z

5

How about this?

_.all(needed_permissions, function(v){
    return _.include(given_permissions, v);
});

answered Aug 1, 2012 at 8:28

xiaowl

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Comments

vikeri · Accepted Answer · 2015-05-29 08:54:07Z

2

Late answer but this works for me: _.isEqual(given_permissions, needed_permissions);

answered May 29, 2015 at 8:54

vikeri

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