Array.entries()

The Array.entries() method in JavaScript returns a new Array Iterator object that contains key/value pairs for each index in the array. The keys are the array indices, and the values are the corresponding array elements.

Syntax

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array.entries()

Parameters

The entries() method does not take any parameters.

Return Value

The entries() method returns a new Array Iterator object. Each item in the iterator is a two-element array, where the first element is the array index (key) and the second element is the array value.

Examples

1. Iterating Over an Array with entries()

This example demonstrates how to use the entries() method to iterate over an array’s key-value pairs.

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const fruits = ["apple", "banana", "cherry"];

const iterator = fruits.entries();

for (const [index, value] of iterator) {
  console.log(index, value);
}

Output

0 apple
1 banana
2 cherry
  1. iterator provides key-value pairs from the array.
  2. Using for...of, each index and value pair is destructured and logged to the console.

2. Converting an Iterator to an Array

The returned iterator can be converted into an array using the Array.from() method.

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const fruits = ["apple", "banana", "cherry"];

const entriesArray = Array.from(fruits.entries());
console.log(entriesArray);

Output

[ [ 0, 'apple' ], [ 1, 'banana' ], [ 2, 'cherry' ] ]
  1. Array.from() converts the iterator returned by entries() into an array of key-value pairs.
  2. Each sub-array contains the index as the first element and the value as the second.

3. Using entries() in a Map-Like Structure

The entries() method can be useful when treating arrays like maps or dictionaries.

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const scores = [10, 20, 30];

for (const [key, value] of scores.entries()) {
  console.log(`Player ${key + 1}: ${value} points`);
}

Output

Player 1: 10 points
Player 2: 20 points
Player 3: 30 points
  1. The entries() method returns each index-value pair.
  2. The for...of loop is used to format and log the output for each player.