Array.prototype.unshift
Adds the specified elements to the beginning of an array and returns the new length of the array
Syntax
array.unshift(...elements)Parameters
| Parameter | Type | Description |
|---|---|---|
| elements | T[] | Elements to add to the front of the array |
Return Value
The new length of the array
Examples
const arr = [1, 2, 3];
arr.unshift(0);
console.log(arr); // [0, 1, 2, 3]const arr = [4, 5, 6];
arr.unshift(1, 2, 3);
console.log(arr); // [1, 2, 3, 4, 5, 6]const queue: string[] = ['b', 'c'];
queue.unshift('a');
console.log(queue); // ['a', 'b', 'c']Understanding Array.prototype.unshift
The Array.prototype.unshift method in JavaScript adds the specified elements to the beginning of an array and returns the new length of the array. It belongs to the Array object and is one of the most widely used methods for working with array values in modern JavaScript and TypeScript applications.
The method signature is array.unshift(...elements). It accepts 1 parameter: elements. When called, it returns the new length of the array. Understanding when and how to use unshift() helps you write more expressive, readable code.
Common use cases for Array.prototype.unshift include data transformation, input validation, API response processing, and building reusable utility functions. It works well alongside related methods like array-shift, array-push, array-pop, enabling you to chain operations together for complex data manipulation pipelines.
Browser support for Array.prototype.unshift is excellent across all modern browsers including Chrome, Firefox, Safari, and Edge. It is also fully supported in Node.js and Deno. For older environments, transpilation with Babel or a polyfill may be needed.
Browser Compatibility
Supported in all modern browsers (Chrome, Firefox, Safari, Edge) and Node.js. Part of the ECMAScript standard.
Related Methods
Array.prototype.shiftRemoves the first element from an array and returns that removed element, changing the length of the array
Array.prototype.pushAdds the specified elements to the end of an array and returns the new length of the array
Array.prototype.popRemoves the last element from an array and returns that element, changing the length of the array
Array.prototype.spliceChanges the contents of an array by removing or replacing existing elements and/or adding new elements in place
More Array Methods
Other methods in the Array object
Related Tools
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