How to merge two arrays in JavaScript
Łukasz Holeczek
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Merging arrays is essential when combining data from multiple sources, concatenating user selections, or building unified datasets in JavaScript applications. With over 25 years of experience in software development and as the creator of CoreUI, I’ve implemented array merging extensively in components like multi-select filters, data aggregation systems, and navigation builders where multiple arrays need to be combined. From my extensive expertise, the most modern and efficient solution is using the ES6 spread operator, which creates a new array without mutating the original arrays. This approach is clean, readable, and performs well for most use cases.
How to check if an array contains a value in JavaScript
Łukasz Holeczek
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Checking whether an array contains a specific value is fundamental for validation, conditional logic, and user interface states in modern JavaScript applications.
With over 25 years of experience in software development and as the creator of CoreUI, I’ve implemented this check thousands of times in components like permission systems, feature toggles, and form validation where specific values determine application behavior.
From my extensive expertise, the most modern and efficient solution is using the ES6 includes() method, which provides a clean boolean return value.
This approach is readable, performant, and specifically designed for membership testing.
How to add an item to an array in JavaScript
Łukasz Holeczek
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Adding items to arrays is one of the most fundamental operations in JavaScript development, essential for building dynamic user interfaces and managing data collections.
As the creator of CoreUI, a widely used open-source UI library, I’ve implemented array manipulation countless times in components that handle dynamic lists, navigation menus, and data tables.
From my expertise, the most efficient and widely supported method is using the push() method to add items to the end of an array.
This approach is performant, intuitive, and works consistently across all JavaScript environments.