Change array element in Javascript

A array element can be changed by providing new value at specified index value. It changes the value of array element only if its valid index in the array. If the index value is higher than array length it adds new element in the array. If there is any gap in between array length and specified index, it will adds empty element with undefined value in between to fill the array gap.

Change array element

 1 // define array
 2 let arr = [10, 20, 30];
 3 	
 4 // change existing array element value
 5 arr[2] = 40; // udpated array element [10, 20, 40]
 6 	
 7 // change non existing array element
 8 arr[5] = 100; // updated array element [10, 20, 40, undefined, undefined, 100]
 9 	
 10 	
 11 // display array element using for-of loop
 12 for(element of array) {
 13    console.log(element);
 14 }

In the above example, we have define array with 3 elements. An array element at position 2 is changed with new value 40. It will update the array element with new value. In the second example, we are updating array element at position 5 which is not present in the array. Hence, rather updating array element at position 5, it will add new element in array.

As array length is 3 and we are updating array at position 5, it adds new element at 5 with value 100 and it also adds 2 new element at index 3 and 4 with value undefined.

Compute square of each elements

 1 let array = [1, 2, 3, 4, 5];
 2 
 3 // print original array
 4 console.log("Original array : ", array);
 5 
 6 // square of each elements
 7 for(i = 0; i < array.length; i++) {
 8     array[i] = array[i] * array[i];
 9 }
 10 // print updated array
 11 console.log("Square of each elements :", array);

In the above example, an array is define and initialized with number values. An array is iterated using for loop and length property of array. An array elements are re-initialized by computing a square of each elements and printed.

Output

 1 Original array :  [ 1, 2, 3, 4, 5 ]
 2 Square of each elements : [ 1, 4, 9, 16, 25 ]

Convert each elements of string array to uppercase

 1 let array = ["Hello", "World", "in", "IOGyan"];
 2 
 3 // print original array
 4 console.log("Original array : ", array);
 5 
 6 // convert uppercase
 7 for(i = 0; i < array.length; i++) {
 8     array[i] = array[i].toUpperCase();
 9 }
 10 // print updated array
 11 console.log("Uppercase elements :", array);

In the above example, an array is define and initialized with string literals. An array is iterated using for loop and length property of array. An array elements are re-initialized by converting each string element into uppercase using string method toUpperCase() and printed.

Output

 1 Original array :  [ 'Hello', 'World', 'in', 'IOGyan' ]
 2 Uppercase elements : [ 'HELLO', 'WORLD', 'IN', 'IOGYAN' ]

Related options for your search

NumPy reverse array in Python

List method append() in Python

Modify dictionary value in Python

Object method freeze() in Javascript

Object method isFrozen() in Javascript

Object method preventExtensions() in Javascript

Object method seal() in Javascript

Object method defineProperty() in Javascript

Object Property descriptor option writable in Javascript

Set date values (methods) in Javascript

Event change in Javascript

Event durationchange in Javascript

Event fullscreenchange in Javascript

Event hashchange in Javascript

Event input in Javascript

Event onratechange in Javascript

Event volumechange in Javascript

HashChangeEvent object in Javascript

Property binding in angular

Disclaimer

About us