JavaScript

Range Generator

by @admin

12h ago

Apr 28, 2026

Public

Generates an array of numbers from start to end (inclusive) with an optional step. Supports negative steps for counting down. Covers the most common use case of Array.from({ length: n }, (_, i) => i) with a much cleaner API, and handles arbitrary start/end/step combinations.

JavaScript

function range(start, end, step = 1) {
  const result = [];
  if (step === 0) throw new Error('step cannot be 0');
  for (let i = start; step > 0 ? i <= end : i >= end; i += step) {
    result.push(i);
  }
  return result;
}

// Usage
console.log(range(1, 5));        // [1, 2, 3, 4, 5]
console.log(range(0, 10, 2));   // [0, 2, 4, 6, 8, 10]
console.log(range(5, 1, -1));   // [5, 4, 3, 2, 1]

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