alert-or.md

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<a href="../logical-operators.html" Logical operators

<a href="../logical-operators.html"

What's the result of OR'ed alerts?

importance: 3

What will the code below output?

alert( alert(1) || 2 || alert(3) );

solution

The answer: first 1, then 2.

<a href="alert-or.html#"

alert( alert(1) || 2 || alert(3) );

The call to alert does not return a value. Or, in other words, it returns undefined.

1. The first OR || evaluates its left operand alert(1). That shows the first message with 1.
2. The alert returns undefined, so OR goes on to the second operand searching for a truthy value.
3. The second operand 2 is truthy, so the execution is halted, 2 is returned and then shown by the outer alert.

There will be no 3, because the evaluation does not reach alert(3).