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docs(blog): update every for snippets (#6650)
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Co-authored-by: Batuhan Wilhelm <[email protected]>
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necatiozmen and BatuhanW authored Jan 17, 2025
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Expand Up @@ -4,11 +4,11 @@ description: We expound with examples what the JavaScript every method is, how i
slug: javascript-every-method
authors: abdullah_numan
tags: [javascript]
image: https://refine.ams3.cdn.digitaloceanspaces.com/blog/2022-11-02-js-every/social.png
image: https://refine.ams3.cdn.digitaloceanspaces.com/blog/2022-11-02-js-every/social-2.png
hide_table_of_contents: false
---

**_This article was last updated on February 7, 2024, to reorganize content for clarity and add new 'use cases' sections for the JavaScript 'every' method._**
_**This article was last updated on January 17, 2025, to include best practices for using the JavaScript every method, a detailed table comparing every with some, and tips for avoiding common mistakes when working with sparse arrays, empty arrays, and callbacks involving thisArg.**_

## Introduction

Expand All @@ -23,13 +23,19 @@ In this post, we expound with examples what `Array.prototype.every` is and how i
Steps we'll cover:

- [What is the JavaScript `Array.prototype.every` Method ?](#what-is-the-javascript-arrayprototypeevery-method-)
- [JS `Array.prototype.every`: Details of the Callback Function](#js-arrayprototypeevery-details-of-the-callback-function)
- [How JavaScript Array `every` Method Works](#how-javascript-array-every-method-works)
- [Comparison Table: JavaScript `every` vs `some`](#comparison-table-javascript-every-vs-some)
- [When to Use the JS Array `every` Method](#when-to-use-the-js-array-every-method)
- [JavaScript Array `every()` With `thisArg` Argument](#javascript-array-every-with-thisarg-argument)
- [JavaScript Array `every(callback, thisArg)` Doesn't Work With Arrow Functions](#javascript-array-everycallback-thisarg-doesnt-work-with-arrow-functions)
- [JavaScript Array `every(callback, thisArg)` Works With Non-Arrow Functions](#javascript-array-everycallback-thisarg-works-with-non-arrow-functions)
- [JavaScript Array `every` Method: Modifying the Caller Array](#javascript-array-every-method-modifying-the-caller-array)
- [Nuances of Using JS Array `every` Method](#nuances-of-using-js-array-every-method)
- [The JS `Array.prototype.every`: Using with Sparse Arrays](#the-js-arrayprototypeevery-using-with-sparse-arrays)
- [Using JavaScript `every` With Empty Arrays](#using-javascript-every-with-empty-arrays)
- [Difference Between Some and Every in JavaScript?](#difference-between-some-and-every-in-javascript)
- [When Should You Use the JavaScript every Method?](#when-should-you-use-the-javascript-every-method)

## What is the JavaScript `Array.prototype.every` Method ?

Expand Down Expand Up @@ -75,6 +81,17 @@ console.log(areAllDoubledEven); // true

In the chunk of code above, `even` is our callback function, which we pass to `every()`. Apparently, we have at least one odd number in our `numbers` array and so not all elements pass the test. So, `every()` returns `false` for `areAllEven`. In contrast, all items in `numbersDoubled` are even, so we get `true` for `areAllDoubledEven`.

## Comparison Table: JavaScript `every` vs `some`

| Feature | `every` Method | `some` Method |
| ------------------ | ------------------------------------------ | ---------------------------------------------------- |
| **Purpose** | Tests if **all** elements pass a condition | Tests if **at least one** element passes a condition |
| **Returns** | `true` if all elements pass the test | `true` if any element passes the test |
| **Stops Checking** | At the first failing element | At the first passing element |
| **Empty Arrays** | Always returns `true` | Always returns `false` |

You can now directly copy and paste this table into your Markdown editor!

## When to Use the JS Array `every` Method

The JS Array `every` method can be used in a wide range of scenarios where we need to verify that all items, with no exception, satisfy the test specified in the callback function. In all cases, the first argument (`element`) has to be passed to the callback. The complexity of the test would determine whether to access the second (`index`), third arguments (`array`), or any additional argument via the `thisArg` object.
Expand Down Expand Up @@ -348,6 +365,60 @@ In JavaScript, `some()` returns `true` if any array element meets a condition, w
- Returns `true` only if all elements pass the test, otherwise `false`.
- Stops checking once it finds a failing element.

## When Should You Use the JavaScript every Method?

### Data Validation

Use it to check if all form fields are filled in:

```javascript
const fields = ["[email protected]", "password123"];
const allFieldsFilled = fields.every((field) => field.trim() !== "");
console.log(allFieldsFilled); // true if no empty fields
```

### Check Data Types

Confirm that an array contains only numbers:

```javascript
const data = [1, 2, 3];
const allNumbers = data.every((item) => typeof item === "number");
console.log(allNumbers); // true
```

### Team Permissions

Verify if all team members have admin roles:

```javascript
const team = [{ role: "admin" }, { role: "admin" }];
const allAdmins = team.every((member) => member.role === "admin");
console.log(allAdmins); // true
```

## FAQs About the JavaScript every Method

### 1. What is the purpose of the every method in JavaScript?

This checks whether all the elements in an array pass a test provided in a callback function. If all pass, it returns true; otherwise, false.

### 2. Does the every method work for empty arrays?

Yes, this always returns true for empty arrays since there are no elements that could fail the condition.

### 3. Can the every method modify the array?

No, the method itself doesn't change the array. However, the array can change inside the callback function.

### 4. What is the difference between every and some?

every checks if all elements meet the condition, while some checks if at least one element meets the condition.

### 5. Does the every Method Work with Objects?

Yes, but you would need to access the object properties in the callback function to test them.

## Summary

In this article, we explored in depth the **JavaScript every** which helps us test whether all items in an array pass the test we implement in a callback function. We saw with examples that the callback function can take three arguments, and additional arguments can be bound to its execution context by setting its `this` value with a `thisArg` passed to `every()` as the second argument.
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