Finding Problems in Your JavaScript Code

• Use Firefox Error Console (Tools Error Console)
• Use JS Closure Compiler (JS Closure Compiler)
• Check for commonly found errors
  1. Semicolon after while expression (e.g., while(x < 2); { }
  2. Semicolon after if expression (e.g., if (x < 2) ; { }
  3. Missing ; in for loop
  4. Variable not initialized
  5. Incorrect use of || in expression (e.g., x = 2 || 4)
  6. Using = instead of == or === in expression (e.g., if (x = 2))
  7. Naming local variable after the function
  8. Getting "undefined"?
     • Make sure your functions return a value
     • Make sure your variables are initialized
     • Make sure you are not getting out of the bounds of the array
  9. Array Related
     • Incorrect loop termination expression (e.g., (for (i= 0; i<= a.length; i++))
     • Assuming array duplication is done by assignment (e.g., a = b))
     • Make sure you spell length correctly when accessing the length of an array
     • Make sure you are not getting out of the bounds of the array
• Trace your code using Firebug (http://getfirebug.com/)

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