Comments on: Be careful with JavaScript variable declarations http://www.thunderguy.com/semicolon/2007/07/30/be-careful-with-javascript-variable-declarations/ Software, the Internet and you. Tue, 16 Mar 2010 04:05:30 -0700 http://wordpress.org/?v=2.8.5 hourly 1 By: Software Evolution » Blog Archive » Be careful with JavaScript variable declarations http://www.thunderguy.com/semicolon/2007/07/30/be-careful-with-javascript-variable-declarations/comment-page-1/#comment-44178 Software Evolution » Blog Archive » Be careful with JavaScript variable declarations Tue, 22 Jan 2008 11:25:05 +0000 http://www.thunderguy.com/semicolon/2007/07/30/be-careful-with-javascript-variable-declarations/#comment-44178 [...] More: continued here [...] [...] More: continued here [...]

]]> By: Bennett http://www.thunderguy.com/semicolon/2007/07/30/be-careful-with-javascript-variable-declarations/comment-page-1/#comment-37648 Bennett Tue, 18 Sep 2007 09:38:04 +0000 http://www.thunderguy.com/semicolon/2007/07/30/be-careful-with-javascript-variable-declarations/#comment-37648 Well, of course this is mandatory in C and C++ since they make no such guarantees. I agree with you in the case of Java because it silently initialises variables to a plausible value (e.g. 0 for numeric variables) which might therefore be used by accident if you forget to initialise it properly. But in dynamically-typed languages like JavaScript it makes less sense since variables are initialised to a special value (<code>undefined</code>) -- if it gets used by accident then the error will be immediately obvious. Having said that, it doesn't hurt to put "<code>= 0</code>" or "<code>= ""</code>", does it? Well, of course this is mandatory in C and C++ since they make no such guarantees. I agree with you in the case of Java because it silently initialises variables to a plausible value (e.g. 0 for numeric variables) which might therefore be used by accident if you forget to initialise it properly.

But in dynamically-typed languages like JavaScript it makes less sense since variables are initialised to a special value (undefined) — if it gets used by accident then the error will be immediately obvious.

Having said that, it doesn’t hurt to put “= 0” or “= ""“, does it?

]]> By: Greg http://www.thunderguy.com/semicolon/2007/07/30/be-careful-with-javascript-variable-declarations/comment-page-1/#comment-37590 Greg Mon, 17 Sep 2007 13:07:54 +0000 http://www.thunderguy.com/semicolon/2007/07/30/be-careful-with-javascript-variable-declarations/#comment-37590 Regardless of the guarantees that modern C, C++, and Java give about clearing memory when declaring a variable, it is always good practice to set a variable unconditionally before reading from it. This is as much for program readability as it is for avoiding problems like the case you bring up. Regardless of the guarantees that modern C, C++, and Java give about clearing memory when declaring a variable, it is always good practice to set a variable unconditionally before reading from it. This is as much for program readability as it is for avoiding problems like the case you bring up.

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