Iterating over an Object to verify if it's keys exist in an Array

Question

Heres the situation -

I have an Array and an Object.

say:

var Array = ["field1", "field2", "field3"];
var Object = { field1: undefined, field2: undefined, field3: undefined, field4: undefined, field5: undefined}

*the values in the object don't really matter right now

Using underscoreJS i want to iterate over the Object and check to see if each of the keys exists in the Array array. If it does i want to be able to set its value to true and if not i want to set it to false.

So far i've tried:

 _.mapObject(Object, function(val, key){

        for (var j = 0; j < Array.length; j++) {
            currentKey = Array[j];
            (function(i){
                for (var k = 0; k < Array.length; k++) {
                    if(key === Array[i]) {
                        return val = true;
                    } else {
                        return val = false;
                    }
                }
            })(currentKey);
        }

    });

Shit is very confusing; for me at least. Any help is appreciatated.

It's a very bad idea to name your objects Object and your arrays Array, as that are the built-in class* names and you're likely to get lots of funny errors later. Instead, how about obj and arr? — phihag
– phihag, Commented May 5, 2016 at 17:23
You must not return false if only one of the keys is not the same. — Bergi
– Bergi, Commented May 5, 2016 at 17:24

Gruff Bunny · Accepted Answer · 2016-05-05 17:52:50Z

1

Here's a solution using underscore:

    var result = _.mapObject(Object, function(value, field){
        return _.contains(Array, field);
    });

or if you want to change Object itself:

    var result = _.each(Object, function(value, field){
        return _.contains(Array, field);
    });

answered May 5, 2016 at 17:52

Gruff Bunny

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1 Comment

Avant Baker Over a year ago

Thank you so much @Gruff bunny!

Ruslan Osmanov · Accepted Answer · 2016-05-05 17:28:31Z

1

I don't think you need underscore for this:

var a = ["field1", "field2", "field3"];
var o = { field1: undefined, field2: undefined, field3: undefined, field4: undefined, field5: undefined}

for (var k in o) {
  o[k] = a.indexOf(k) != -1;
}

answered May 5, 2016 at 17:28

Ruslan Osmanov

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Comments

ste2425 · Accepted Answer · 2016-05-05 17:38:32Z

1

As others have said there's no need for underscore.

You can use the native Object.keys to return an array of own keys then iterate over them. Object.keys will not include inherited properties from the prototype chain which for in will. It is however considerably slower which could be a problem with large data-sets.

Object.keys(obj)
    .forEach(function (key) {
        obj[key] = (arr.indexOf(key) !== -1);
    });

Fiddle

Object.keys

edited May 5, 2016 at 17:38

answered May 5, 2016 at 17:33

ste2425

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Comments

t1m0n · Accepted Answer · 2016-05-05 17:26:23Z

0

You don't need underscore to do this:

var arr = ['a','b','c'],
        obj = {a: '', b: '', c: '', d:''};

function check (a, o) {
    for (var key in o) {
        if (a.indexOf(key) != -1) {
            o[key] = true
        }
    }
}

check(arr,obj);

document.write(JSON.stringify(obj))

answered May 5, 2016 at 17:26

t1m0n

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