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Stu Finn
Stu Finn

Posted on • Updated on

How to iterate over objects using array methods

Arrays are so freaking handy! They are a great way to store data and they have some really amazing “array methods” like .forEach() and .map() (and more) that allow us to easily iterate over an array. Sweet!

const sampleArray = [I, love, technology];

sampleArray.forEach( (word) => {

// I
// love
// technology
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Objects are super too, in my humble opinion. With key/value pairs we only need a key name and we can get the associated value.

const sampleObject = {
    word1: "Always",
    word2: "and",
    word3: "forever"

// We can use either dot- or bracket-notation to access values:

console.log(sampleObject.word1);    // Always

console.log(sampleObject['word3']);    // Forever
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What seems less awesome, though, is that array methods like .forEach(), .map(), etc… don’t work on objects. Noooooo!

[Insert sad-face here]

But don’t despair! There is a way to use array methods to easily iterate over objects, using the Object.keys() method. Let me explain:

What's Object.keys( ), you say?

Object.keys() is a built in Javascript method that takes any object as a parameter, and returns an array of that object’s keys.

For example:


//  [“word1”, “word2”, “word3”] 
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Right on!

So as a workaround, we can use the returned array of keys to iterate over our object using an array method such as .forEach(). Sick!

Let me show you:

// here we now have an array of sampleObject’s keys
const arrayOfKeys = Object.keys(sampleObject);  

// we can use the key to call up each piece of Object data 
arrayOfKeys.forEach( key => console.log( sampleObject[key] ); 

// Always
// and
// forever
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WHAAAAAT?! Beautiful! *wipes away a single tear*

Now you know how to easily iterate over an Object using at least one array method. Please use your new powers responsibly!

I love technology

  • For more information on array methods see the MDN webdocs.

  • To learn about some of the best array methods out there, check out this handy article.

Many thanks to Wes Bos for pointing this out in his React for Beginners course. It's a really great course.

Top comments (8)

wintercounter profile image
Victor Vincent

How about:

for (const [key, value] of Object.entries(obj)) {
    console.log(key, value)

So much cleaner! People usually just scratching the surface of what JS can actually do.

robaxelsen profile image
Robert Axelsen • Edited

Beautiful! This one is also nice:

Object.entries(obj).forEach(([key, value]) => {
  console.log(key, value);
schester44 profile image
Steve Chester

Object.keys holds a special place in my heart. You can also use Object.entries as well.

msinkgraven profile image
Matthew Sinkgraven

Don't forget Object.values ;)

kenotron profile image
Kenneth Chau

sampleObject[word3] should be sampleObject['word3'], eh?

stu profile image
Stu Finn

You're right! Ah, thanks for catching that - fixed now. Cheers

the_riz profile image
Rich Winter

"New", but...

and while you have to know some about the enumerable properties of the object and its prototype-
for(let i in obj){ ... }

wintercounter profile image
Victor Vincent

That's why there is for-of