snippetjavascriptTip

Iterate over a JavaScript object's own properties

Submitted by: @import:30-seconds-of-code·Mar 2, 2026·

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javascriptobjectiterateoverownproperties

Problem

Array.prototype.forEach() is a great way to iterate over an array, but it doesn't work for objects. However, with a little help from Object.keys(), we can easily create our own object property iterator.
As mentioned already, we simply need to use Object.keys() to get all the properties of the object and then use Array.prototype.forEach() to run the provided function for each key-value pair. The callback should receive three arguments - the value, the key and the object itself.
If you need to iterate over the object properties in reverse, you can use Array.prototype.reverse() to reverse the order of the keys before iterating over them.
> [!WARNING]
>

Solution

const forOwn = (obj, fn) =>
  Object.keys(obj).forEach(key => fn(obj[key], key, obj));

forOwn({ foo: 'bar', a: 1 }, v => console.log(v));
// Logs: 'bar', 1

If you need to iterate over the object properties in reverse, you can use Array.prototype.reverse() to reverse the order of the keys before iterating over them.
> [!WARNING]
>
> The order of the resulting keys may not match the order of the original keys, as JavaScript objects are unordered. All examples in this article assume that the original order is preserved.

Code Snippets

const forOwn = (obj, fn) =>
  Object.keys(obj).forEach(key => fn(obj[key], key, obj));

forOwn({ foo: 'bar', a: 1 }, v => console.log(v));
// Logs: 'bar', 1

const forOwnRight = (obj, fn) =>
  Object.keys(obj)
    .reverse()
    .forEach(key => fn(obj[key], key, obj));

forOwnRight({ foo: 'bar', a: 1 }, v => console.log(v));
// Logs: 1, 'bar'

Context

From 30-seconds-of-code: iterate-object-properties

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