Array.every() Method
Tags: webdev, javascript, beginners, programming
Published: 2023-06-18 16:01:09

## What is Every Method?

The `every()` tests whether all elements in the array pass the test implemented by the provided function. It returns a Boolean value.

## Syntax

Here's the syntax for using `every()`:

```js
const result = arr.every((element, index, array) => {
	// Return true if all elements pass the test, false otherwise
});
```

The `callback` function is called for each element in the array and takes the following arguments:

- `element`: the current element being processed in the array
- `index` (optional): the index of the current element
- `array` (optional): the array that every() is being applied to

The `every()` method calls the `callback` function once for each element in the array, in order, and stops when it finds an element for which the callback returns `false`. If such an element is found, the method returns `false`. Otherwise, if the callback returns `true` for all elements, `every()` returns `true`.

Here's an example of how to use `every()` to check if all the numbers in an array are even:

```js
const numbers = [2, 4, 6, 8, 10];

const result = numbers.every(function (number) {
	if (number % 2 === 0) {
		return true;
	} else {
		return false;
	}
});

console.log(result); // prints true
```

In the example above, the callback function is an `anonymous` function that takes a single argument, number, and returns `true` if number is even, and `false` otherwise. The `every()` method calls this function for each element in the `numbers` array and stops when it finds an odd number. Since all the numbers in the array are even, the `every()` method returns `true`.

You can also use an arrow function as the callback function, like this:

```js
let result = numbers.every((number) => number % 2 === 0);

console.log(result); // prints true
```

The `every()` method is useful for checking if all the elements in an array pass a certain condition.

## Examples

Here are a few more examples of how you can use `every()`:

### Checking if all the numbers in an array are greater than 10

```js
const numbers = [12, 14, 16, 18, 20];

const result = numbers.every((number) => number > 10);

console.log(result); // prints true
```

### Checking if all the strings in an array are of a certain length

```js
const strings = ["hello", "world", "this", "is", "javascript"];

const result = strings.every((string) => string.length > 5);

console.log(result); // prints false
```

### Checking if all the elements in an array are of a certain type

```js
const mixedArray = [1, 2, 3, "hello", "world", true, false];

const result = mixedArray.every((element) => typeof element === "number");

console.log(result); // prints false
```

### Checking if student is passed in all subjects

```js
const ross = {
	name: "Ross",
	age: 14,
	class: 8,
	subjects: [
		{ name: "Math", score: 90 },
		{ name: "Computer", score: 50 },
		{ name: "English", score: 80 },
		{ name: "Social Science", score: 60 },
		{ name: "Science", score: 70 },
	],
};

const result = ross.subjects.every((subject) => subject.score >= 60);

console.log(result); // prints false
```

### Checking if all the elements in an array are unique

```js
const numbers = [1, 2, 3, 4, 5];

const result = numbers.every((number, index, array) => {
	return array.indexOf(number) === index;
});

console.log(result); // prints true
```

## When to use Every Method?

The `every()` method is useful for checking if all the elements in an array pass a certain condition. It returns `true` if all the elements pass the test, and `false` otherwise. For example:

```js
const numbers = [12, 14, 16, 18, 20];

const result = numbers.every((number) => number > 10);

console.log(result); // prints true
```

In the example above, the `every()` method checks if all the numbers in the `numbers` array are greater than 10. Since all the numbers in the array are greater than 10, the `every()` method returns `true`.

## Conclusion

In this article, we learned about the `every()` method. We learned about its syntax, how to use it, and when to use it. We also learned about a few examples of how to use it.