Javascript Array entries()

// defining an array named alphabets
const alphabets = ["A", "B", "C"];

// array iterator object that contains
// key-value pairs for each index in the array
let iterator = alphabets.entries();

// iterating through key-value pairs in the array
for (let entry of iterator) {
  console.log(entry);
}

// Output: 
// [ 0, 'A' ]
// [ 1, 'B' ]
// [ 2, 'C' ]

entries() Syntax

The syntax of the entries() method is:

arr.entries()

Here, arr is an array.

entries() Parameters

The entries() method does not take any parameters.

entries() Return Value

• Returns a new Array iterator object.

Note: The entries() method does not change the original array.

Example 1: Using entries() Method

// defining an array 
const languages = ["Java", "C", "C++", "Python"];

// array iterator object that contains
// key-value pairs for each index in the array
let iterator = languages.entries();

// looping through key-value pairs in the array
for (let entry of iterator) {
  console.log(entry);
}

Output

[ 0, 'Java' ]
[ 1, 'C' ]
[ 2, 'C++' ]
[ 3, 'Python' ]

In the above example, we have used the entries() method to get an Array iterator object of the key/value pair of each index in the language array.

We have then looped through iterator that prints the key/value pairs of each index.

Example 2: Using next() Method in Array Iterator Object

Array Iterator object has a built-in method called next() which is used to get the next value in the object.

Instead of looping through the iterator, we can get the key/value pairs using next().value. For example:

// defining an array
const symbols = ["#", "$", "*"];

// Array iterator object that holds key/value pairs 
let iterator = symbols.entries();

// using built-in next() method in Array iterator object
console.log(iterator.next().value);
console.log(iterator.next().value);
console.log(iterator.next().value);

Output

[ 0, '#' ]
[ 1, '$' ]
[ 2, '*' ]

Recommended Reading: JavaScript Array keys()