Using a block’s return value in JavaScript

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In JavaScript, statements return values of the Completion type (which is not a language type, but a specification type).

The Completion type is used to explain the behaviour of statements
(break, continue, return and throw) that perform nonlocal transfers of
control. Values of the Completion type are triples of the form (type,
value, target), where type is one of normal, break, continue, return,
or throw, value is any ECMAScript language value or empty, and target
is any ECMAScript identifier or empty.

Source: http://es5.github.com/x8.html#x8.9

So, eval() evaluates the program that has been passed in as source text. That program (like any JavaScript program) returns a Completion value. The second item in this Completion value (the “value” item) is returned by the eval() invocation.

So, with eval you are able to retrieve the completion value of an JavaScript program. I am not aware of any other method to accomplish this…

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