All browsers that support JavaScript 1.3 which is when the === operator was introduced.
(a === true) evaluates to true given that a is true.
And because true is exactly the same as true the behaviour is exactly the same.
So examples of browsers that don’t support JavaScript are can be seen of this page: http://en.wikipedia.org/wiki/Comparison_of_web_browsers#JavaScript_support
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solved Browser support for certain if statements [closed]