Building a Zero-Dependency Random String Generator for Node.js (With Secure Mode)

Generating random strings is one of those things every backend developer ends up doing — IDs, tokens, session keys, you name it. But while working on this, I realized most implementations fall into a few common traps: Using Math.random() everywhere (not secure) Inefficient "generate + filter" logic Pulling heavy dependencies for a simple problem So I decided to build a clean solution from scratch — and learned a few interesting things along the way. ❌ The Common Mistake A lot of implementations generate from a full alphanumeric charset and then filter results using a regex check inside the loop — only keeping characters that match the desired type. This means: Problems: Wastes iterations (filtering) Uses regex inside loops Performance depends on randomness Hard to maintain ✅ A Better Approach Instead of generating and filtering — generate directly from the correct character set. Pre-define separate charsets for alpha, numeric, and alphanumeric, then index into the right one. This elimi