How to Extend an Existing JavaScript Array with Another Array, Without Creating a New Array
As a JavaScript developer, you may often come across situations where you need to extend an existing array with the contents of another array. While there are multiple ways to achieve this, it is important to do so without creating a new array, as it can impact performance and memory usage. In this blog post, we will explore a few solutions to this problem.
Solution 1: Using the push() method
The push() method is a built-in JavaScript function that allows you to add one or more elements to the end of an array. By using this method, you can easily extend an existing array with the contents of another array.
Here’s an example:
const array1 = [1, 2, 3];
const array2 = [4, 5, 6];
array1.push(...array2);
console.log(array1);
The spread syntax (…) is used to spread the elements of array2 into individual arguments for the push() method. This ensures that the elements of array2 are added to array1 as separate elements, rather than as a nested array.
The output of the above code will be:
[1, 2, 3, 4, 5, 6]Solution 2: Using the concat() method
The concat() method is another built-in JavaScript function that allows you to merge two or more arrays into a new array. However, we can use it in a slightly different way to extend an existing array without creating a new array.
Here’s an example:
const array1 = [1, 2, 3];
const array2 = [4, 5, 6];
Array.prototype.push.apply(array1, array2);
console.log(array1);
In this solution, we are using the apply() method to apply the push() method of the Array prototype to array1. This effectively extends array1 with the elements of array2.
The output of the above code will be the same as the previous solution:
[1, 2, 3, 4, 5, 6]Conclusion
Extending an existing JavaScript array with another array is a common requirement in many JavaScript applications. By using the push() method or the apply() method in combination with the push() method, you can easily achieve this without creating a new array. This ensures optimal performance and memory usage in your code.
Remember to choose the solution that best fits your specific use case and coding style. Happy coding!
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