Why does JSLint tell me to use “=== undefined” instead of “typeof … === 'undefined'”?

Question

I coded the following:

showTitles = (typeof showTitles !== \'undefined\') ? showTitles : \'Y\';
showSelectGroup = (typeof showSelectGroup !== \'undefined\')          


        

Answer 1

This message reflects the latest best practices. As of ES5 strict mode, the global value of undefined can no longer be changed and a direct comparison is simpler code and faster. In short, JSLint is aware of all this, and is giving you good advice.

In this case, change typeof showTitles !== 'undefined' to showTitles === undefined.