JavaScript Program to Create an Array with a Specific Length and Pre-filled Values
In JavaScript, we can create an array with a specific length and pre-filled values using various approaches. This can be useful when we need to initialize an array with default or placeholder values before populating it with actual data.
Table of Content
- Using the Array() Constructor and fill() Method
- Using a Loop to Initialize Values
- Using the map() Method
- Using Array.from with a Mapping Function
Method 1: Using the Array() Constructor and fill() Method
The Array constructor can be used to create an array of a specific length. The fill() method can fill this array with a specified value.
Syntax:
const filledArray = new Array(length).fill(value);
Example: Below is the implementation of the above approach
const length = 5;
const value = 5;
const filledArray = new Array(length).fill(value);
console.log(filledArray);
Output
[ 5, 5, 5, 5, 5 ]
Method 2: Using a Loop to Initialize Values
We can use a loop to iterate through the desired length and assign values.
Syntax:
const filledArray = Array.from();
for (let i = 0; i < length; i++) {
filledArray.push(value);
}
Example: Below is the implementation of the above approach
const length = 5;
const filledArray = new Array();
for (let i = 0; i < length; i++) {
filledArray.push(i + 1);
}
console.log(filledArray);
Output
[ 1, 2, 3, 4, 5 ]
Method 3: Using the map() Method
The map() method can be used to create an array by applying a function to each element.
Syntax:
const filledArray = Array.from({ length }).map(() => value);
Example: Below is the implementation of the above approach
const length = 5;
const filledArray =
Array.from({ length })
.map(() => 5);
console.log(filledArray);
Output
[ 5, 5, 5, 5, 5 ]
Using Array.from with a Mapping Function
Using Array.from with a mapping function, you can create an array of a specific length with pre-filled values. The mapping function defines the values to fill the array. This approach offers concise and flexible syntax for generating arrays with custom initial values.
Example: In this example we generates a new array filledArray of length 5, filled with the value 0 using Array.from() and an arrow function. It then logs filledArray to the console.
const length = 5;
const value = 0;
const filledArray = Array.from({ length }, () => value);
console.log(filledArray);
Output
[ 0, 0, 0, 0, 0 ]