📓 JavaScript Basics

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Map and Reduce

2025-06-02 05:29

Map and Reduce

Map and Reduce are functional programming methods used to process and transform data collections like arrays or lists.

Map transforms each item in a list and returns a new list. Reduce combines all items in a list into a single value, like a total or result.

// Map Syntax 
array.map(function(currentValue, index, array) { 
// return transformed value 
}); 

// Reduce Syntax 
array.reduce(function(accumulator, currentValue, index, array) { 
// return new accumulator value 
}, initialValue);

// Example: Map - Multiply each number by 2 
const numbers = [1, 2, 3, 4]; 
const doubled = numbers.map(num => num * 2); 
console.log(doubled); // [2, 4, 6, 8] 

// Example: Reduce - Sum all numbers 
const total = numbers.reduce((sum, num) => sum + num, 0); 
console.log(total); // 10