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Ways of iterating over a array in JavaScript.

  • Last Updated : 19 Feb, 2019

Arrays in Javascripts, are single variables used to store different kind of elements.

For example, a simple array accesses may something like this:




<script>
array = [ 'geeks', '4', 'geeks' ];
  
// Accessing array elements one by one
console.log(array[0]);
console.log(array[1]);
console.log(array[2]);
</script>

Output:

geeks
4
geeks

There are multiple ways one can iterate over an array in Javascript. The most useful ones are mentioned below.

Using for loop.
This is similar to for loops in other languages like C/C++, Java, etc






<script>
array = [ 1, 2, 3, 4, 5, 6 ];
for (index = 0; index < array.length; index++) {
    console.log(array[index]);
}
</script>

Output:

1
2
3
4
5
6

Using while loop.
This is again similar to other languages.




<script>
index = 0;
array = [ 1, 2, 3, 4, 5, 6 ];
  
while (index < array.length) {
    console.log(array[index]);
    index++;
}</script>

Output:

1
2
3
4
5
6

using forEach method.
The forEach method calls the provided function once for every array element in the order.




<script>
index = 0;
array = [ 1, 2, 3, 4, 5, 6 ];
  
array.forEach(myFunction);
function myFunction(item, index)
{
    console.log(item);
}</script>

Output:

1
2
3
4
5
6

Using every method.
The every() method checks if all elements in an array pass a test (provided as a function).




<script>
index = 0;
array = [ 1, 2, 3, 4, 5, 6 ];
  
const under_five = x => x < 5;
  
if (array.every(under_five)) {
    console.log('All are less than 5');
}
else {
    console.log('At least one element is not less than 5');
}
</script>

Output:

At least one element is not less than 5.

Using map.
A map applies a function over every element and then returns the new array.




<script>
index = 0;
array = [ 1, 2, 3, 4, 5, 6 ];
  
square = x => Math.pow(x, 2);
squares = array.map(square);
console.log(array);
console.log(squares);</script>

Output:

1 2 3 4 5 6 
1 4 9 16 25 36



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