Is there any difference between the following two snippets, or any reason to use one over the other?
if (foo) {
bar();
}
foo && bar();
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The 1st is more traditional. Effectively, they're the same, though. – Jonathan Lonowski Jul 28 '13 at 12:05
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No difference but I prefer one line `if` statements. `if (foo) bar();` – elclanrs Jul 28 '13 at 12:05
3 Answers
14
The second form is known as short-circuit evaluation and results in exactly the same as the first form. However the first form is more readable and should be preferred for maintainability.
This type of short-cuircuit evaluation is often seen in if-statements, where the right hand is conditionally evaluated. See the example below; bar is only evaluated if foo evaluates to true.
if (foo && bar()) {
// ...
}
Bouke
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It is not exactly the same, in the sense of grammar. (*expression* vs *statement*) – user123444555621 Jul 28 '13 at 12:48
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The version foo && bar() is an expression, and thus has a value:
var result = foo && bar();
When using the if version, the above might look like this:
var result;
if (foo) {
result = bar();
}
which is more verbose.
user123444555621
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1Actually `foo && bar();` is a statement, not expression, `foo && bar()` is an expression. – zch Jul 28 '13 at 13:08
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@zch Correct. It is an [expression statement](http://es5.github.io/#x12.4). – user123444555621 Jul 28 '13 at 13:22
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the if-version is not correct; if foo is falsy, that falsy value is returned. Thus `else { result = foo; }`. – Bouke Jul 29 '13 at 06:44
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The answer of bouke with the short-cuircuit evaluation is really good. But I like to add that a good coding style is the use of the if-statement, if the call of bar() has no boolean-return-value and no further condition has to be satisfied using bar().
Mr.Mountain
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