JavaScript: what is "this"?

Re:JavaScript: what is "this"? by sesqu on Monday March 22, 2010 @08:39AM (#1210151)

The var statement declares a variable as local to the current scope and the entire current scope, not just from the var statement onward. These local variables shadow any existing variables from outer scopes.

Err, I tested this on Chrome's Inspector console, and I don't see such behaviour. The article says name should be undefined at the time of the comparison in the below code, but it isn't (and I frankly can't see why anyone would want it to be). Is this a feature of my execution environment, or have I just completely misunderstood what the author means?

  (function(name){var cmp=name=="tim"; var name; return cmp})("tim") // returns true

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Re:JavaScript: what is "this"? by papercrane on Monday March 22, 2010 @10:00AM (#1210302)

Since the comparison happens before var is declared, it will always evaluate to 'true'. I believe the author was thinking about something like so:

    (function(name) { var cmp = function() { return name=="tim"; }; var name; return cmp();})("tim");

This still evaluates to true, but I believe it has to do with the rules of shadowing. If you change the declaration to 'var name="bob";' it will return false.

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Re:JavaScript: what is "this"? by creationix on Monday March 22, 2010 @10:24AM (#1210352)

Good catch, I'm looking into this one. I know I've seen this behavior before in some JS environment. I'm glad it's not the case for V8 and will shortly update the article.

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