Javascript Array Prepend Easy and Efficient Method

Javascript Array Prepend – Easy and Efficient Method

Javascript Array Prepend – Easy and Efficient Method


Javascript Array Prepend is a method of adding one or more elements at the beginning of an existing array. This method is important for various use cases and is a fundamental tool to manipulate arrays in Javascript.

Understanding Javascript Arrays

Arrays in Javascript are a type of object that store a collection of data items. They can accommodate values of different data types such as numbers, strings, objects, and even other arrays. Arrays in Javascript are zero-indexed, which means the first element of the array is stored with an index of 0.

The Need for Prepending

There are several use cases where we need to add elements at the beginning of an existing array. For instance, it is used in creating a history stack or a queue data structure. It is also used when creating a user interface to display a list of items where the most recent item is to be displayed first.

The unshift() Method

The unshift() method is a built-in array method in Javascript that adds one or more elements to the beginning of an array. The syntax for using the unshift() method is:

array.unshift(element1, ..., elementN)


The unshift() method takes one or more elements to add at the beginning of the array. It can accept any number of arguments, and each argument represents the item to be added to the array.

Return Value

The unshift() method returns the new length of the modified array, which is equal to the original length plus the number of elements added.

Examples of using unshift()

Here are some examples of using the unshift() method:

Using unshift() with single elements

The following example demonstrates how to use the unshift() method to add a single element to the beginning of an array:

let fruits = ['apple', 'banana', 'orange'];
console.log(fruits); // Output: ['mango', 'apple', 'banana', 'orange']

Using unshift() with multiple elements

Adding multiple elements can also be done using the unshift() method:

let numbers = [4, 5, 6];
numbers.unshift(1, 2, 3);
console.log(numbers); // Output: [1, 2, 3, 4, 5, 6]

Calling unshift() on non-array objects

If the unshift() method is called on a non-array object, then it will result in a TypeError.

Performance Comparison

Using the unshift() method is an efficient way to prepend elements to an array as it is a built-in method that has a better time-complexity than other methods such as the splice() method. However, if there are a large number of elements in the array, then the performance may be slower than using other methods such as pushing elements to the end of the array and then reversing the array.

Browser Compatibility

The unshift() method is supported in all modern browsers, including Chrome, Firefox, Safari, Opera, and Microsoft Edge. It is also supported in Internet Explorer 9 and above.


Javascript Array Prepend is an important method that allows users to add elements to the beginning of an array. The unshift() method is an easy and efficient way to accomplish this task. It is important to understand the syntax, parameters, and return value of the unshift() method to be able to use it effectively.

Being a web developer, writer, and blogger for five years, Jade has a keen interest in writing about programming, coding, and web development.
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