Section: Loop Performance - Cache Array Length; global variable. about front-end-development-guidelines HOT 4 CLOSED

Your second example is not even really that safe in terms of scope.

In JavaScript (before 1.7), there is no such thing as block scope. Declaring a variable in a for loop with var will use the scope of its parent function or, in the absence any such containing function, the global scope.

JavaScript 1.7 introduced the let keyword for block scope to be used instead of var. Being a feature of JavaScript 1.7, the let keyword is not ready for general web use as of this time due to lack of support by some browsers, most notably IE.

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The second example throws a JavaScript error, even if I "use strict";

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Well, I feel stupid. Goes to show you should actually test bug reports before submitting them.

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For clarity: http://jsfiddle.net/WuK5w/

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