Why should you care?

Senior developers spend more time debugging than writing new syntax.

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Paste into an HTML file or the browser console (F12). Use Run below when the live editor is available.

function divide(a, b) {
  debugger; // pauses here when DevTools open
  if (b === 0) throw new Error("divide by zero");
  return a / b;
}
console.log(divide(10, 2));

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What happened?

• debugger statement stops if DevTools is open.
• Errors show file and line in console.

Practice next

1. Use debugger statement with DevTools open.
2. Set breakpoint in Sources tab.
3. Step over and into functions.
4. Conditional breakpoint when balance < 0.
5. Log grouped console.group for multi-step checkout trace.

Remember

debugger and breakpoints Read stack traces console methods: log, table, error

ScriptVerse prod incident

Engineer reproduces wrong tax using debugger breakpoint on calculateTax when region is null.

Outcome: Systematic debugging cuts mean time to fix for ScriptVerse payment bugs.