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JavaScript Array entries() Method

By Arvind Rai, November 03, 2019
JavaScript Array entries() method returns a new Array iterator object that contains the key/value pairs for each index in the array. Find the syntax.
array.entries() 
JavaScript Array entries() method is supported by Chrome, Edge, Firefox, Opera, Safari etc. Internet Explorer does not support JavaScript Array entries() method.

Using Array entries() Method

In our example, we have an array and on this array we are calling entries() method that returns a new Array iterator object. By calling iterator next() method, we get the key/value pairs for indexes. In key/value pair, the index is key and value is array element.
var array = ['Mahesh', 'Krishna', 'Brahma'];
var iterator = array.entries();

var el1 = iterator.next();
console.log(el1.value);
var el2 = iterator.next();
console.log(el2.value);
var el3 = iterator.next();
console.log(el3.value); 
Output
[ 0, "Mahesh" ]
[ 1, "Krishna" ]
[ 2, "Brahma" ]

Iterating with for...of loop

The iterator returned by entries() method can be iterated using JavaScript for...of loop.
var array = ['Mangalyaan', 'Chandrayaan', 'Gaganyaan', 'Aditya'];

console.log('--- Fetching key/value pairs ---');

for (const el of array.entries()) {
   console.log(el);
}

console.log('--- Fetching index and element ---');

for (const [index, element] of array.entries()) {
   console.log('Index: ' + index + ', Element: ' + element);
} 
Output
--- Fetching key/value pairs ---
[ 0, "Mangalyaan" ]
[ 1, "Chandrayaan" ]
[ 2, "Gaganyaan" ]
[ 3, "Aditya" ]
--- Fetching index and element ---
Index: 0, Element: Mangalyaan
Index: 1, Element: Chandrayaan
Index: 2, Element: Gaganyaan
Index: 3, Element: Aditya 
Find the print screen of browser console.
Using Array entries() Method

Two-Dimensional Array

Find the example to use entries() method with two-dimensional array.
var array = [
    ['a1', 'b1', 'c1'],
    ['a2', 'b2', 'c2'],
    ['a3', 'b3', 'c3']
];

for (const [index, element] of array.entries()) {
  for (const el of element.entries()) {
    console.log(el);
  }
}
Output
[ 0, "a1" ]
[ 1, "b1" ]
[ 2, "c1" ]
[ 0, "a2" ]
[ 1, "b2" ]
[ 2, "c2" ]
[ 0, "a3" ]
[ 1, "b3" ]
[ 2, "c3" ] 

Reference

Array.prototype.entries()
POSTED BY
ARVIND RAI
ARVIND RAI
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