To change an element in a JavaScript array, use the index number with square brackets []
and assign a new value to it. Arrays are zero-indexed, meaning the first element is at index 0
.
Key Points
- Index Assignment: Use the index to access and change the value.
- Zero-Indexed: The first element is at index
0
.
Examples
Changing an Element
let fruits = ['Apple', 'Banana', 'Orange'];
fruits[1] = 'Mango';
console.log(fruits);
// Output: ['Apple', 'Mango', 'Orange']
Here, we changed the element at index 1
from 'Banana'
to 'Mango'
.
Adding a New Element at a Specific Index
You can also add an element at an index that doesn’t currently have a value:
fruits[3] = 'Grapes';
console.log(fruits);
// Output: ['Apple', 'Mango', 'Orange', 'Grapes']
This adds 'Grapes'
to index 3
of the array.
Practical Tips
Out of Bounds: Adding an element at an index greater than the current length will leave empty slots in between.
fruits[5] = 'Peach';
console.log(fruits);
// Output: ['Apple', 'Mango', 'Orange', 'Grapes', <1 empty item>, 'Peach']
Avoiding Undefined: Be careful when accessing indices that don’t exist, as this will return undefined
.