Declaring a JavaScript Array as const only means that you can’t assign a new value to that variable (Array) once a value has been assigned:
const array = [];
array = []; // Not allowed: assignment to constant variable
Declaring an array as const has no bearing on what you can do with the contents of the actual array:
Using keyword const in Array doesn’t define a constant array. It defines a constant reference to an array.
JavaScript const array
Simple example code.
<!DOCTYPE html>
<html>
<body>
<script>
const arr = [];
arr.push("something"); // Allowed: add value to array
console.log(arr)
arr[0] = "or other"; // Allowed: replace value in array
console.log(arr)
arr.length = 0; // Allowed: change array size
console.log(arr)
</script>
</body>
</html>
Output:
An array declared with const cannot be reassigned:
<script>
const cars = ["A", "B", "C"];
cars = ["X", "Y", "Z"];
</script>Output: Uncaught TypeError: invalid assignment to const ‘cars’
With Object.freeze you can prevent values from being added or changed on the object:
'use strict';
const vector = Object.freeze([1, 2, 3, 4]);
vector[2] = 7; // An element is not constant!How to initialize a JavaScript array with constant values?
Answer:
1: Regular:
var myCars=new Array();
myCars[0]="Saab";
myCars[1]="Volvo";
myCars[2]="BMW";2: Condensed:
var myCars=new Array("Saab","Volvo","BMW");3: Literal:
var myCars=["Saab","Volvo","BMW"];Do comment if you have any doubts or suggestions on this Js Array topic.
Note: The All JS Examples codes are tested on the Firefox browser and the Chrome browser.
OS: Windows 10
Code: HTML 5 Version
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