typescript.regex_compile

Performance High

Detects regex compilation inside loops or hot paths.

Why It Matters

Regex in loops:

• Parses repeatedly — Same pattern compiled per iteration
• Wastes CPU — 10-100x slower than cached
• Hurts latency — Measurable request delays

Example

// ❌ Before (compiling in loop)
for (const line of lines) {
  const match = new RegExp('\\d+').exec(line); // Compiles every iteration!
  if (match) {
    count++;
  }
}

// ✅ After (compile once)
const numberRegex = /\d+/;

for (const line of lines) {
  if (numberRegex.test(line)) {
    count++;
  }
}

What Unfault Detects

• new RegExp() inside loops
• Regex compilation in request handlers
• Dynamic regex patterns that could be static

Auto-Fix

Unfault can hoist regex to module level constants.

Related Rules

• go.regex_compile
• python.regex_compile