What is a good Javascript debugging tool?

Question

Haven\'t touch javascript for 3 years. Just got a javascript project and wanted to know any new ways or tools emerged these years to debug javascript? I used alert 3 years

Answer 1

real programmers use printf() traces for debugging (kidding).

var de =true, bug =console.log||alert||(de=false)

de&&bug( "Enjoy!")

When not in debug mode, just do de=false. Minimal performance penalty