JavaScript Array Methods Cheat Sheet 2025 (Complete Reference)

JavaScript arrays have over 30 built-in methods. Knowing which one to reach for — and understanding the subtle differences between similar methods — is what separates junior developers from experienced ones. This cheat sheet covers every important array method with practical examples, organized by use case. Transformation map(callback) → new array Transform each element into something else. Never mutates the original. const prices = [ 10 , 20 , 30 ]; // Basic transformation const doubled = prices . map ( p => p * 2 ); // [20, 40, 60] // Transform objects const users = [ { id : 1 , firstName : ' Alice ' , lastName : ' Smith ' }, { id : 2 , firstName : ' Bob ' , lastName : ' Jones ' }, ]; const fullNames = users . map ( u => ` ${ u . firstName } ${ u . lastName } ` ); // ['Alice Smith', 'Bob Jones'] // Extract a field (use for select/pluck) const ids = users . map ( u => u . id ); // [1, 2] // Map with index const indexed = [ ' a ' , ' b ' , ' c ' ]. map (( item , i ) => ({ index : i , v