what does the "||" in a var statement mean?

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null coalescing operator for javascript?
What does “options = options || {}” mean in Javascript?

Can someone explain me this expression? I stumbled accros the javascript line of code and I wondered what it means.

var node = element.node || element[element.length - 1].node;

node get's used like this below:

if (node.nextSibling) {
            node.parentNode.insertBefore(this.node, node.nextSibling);
        } else {
            node.parentNode[appendChild](this.node);
        }

At first i though node should be a boolean or something but it's not. Am I correct if i think that the meaning is: node is element.node but if the node attribute is undefined node is the last element in the array of element?

robyaw · Accepted Answer · 2011-10-19T08:47:59.893

5

Your understanding is along the right lines; be aware that even if element.node is defined, but is a falsey value (0, false etc.) that element[element.length - 1].node will be assigned to node instead.

edited Oct 19 '11 at 08:47

answered Sep 16 '11 at 10:55

robyaw

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score 4 · Answer 2 · answered Sep 16 '11 at 10:55

4

It means, if element.node has a value represents True in boolean expressions, node will be element.node, otherwise it will be element[element.length - 1].node

answered Sep 16 '11 at 10:55

sinan

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score 3 · Answer 3 · answered Sep 16 '11 at 10:52

3

Simple answer: it means OR :)

Reference: http://www.w3schools.com/js/js_operators.asp

answered Sep 16 '11 at 10:52

ChrisH

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That part was quite obvious. The real question was: Was kind of weird "or" operation takes objects instead of boolean values and also returns an object instead of a boolean value? How is this "or" defined? Because it certainly isn't the standard definition according to logic. – Weirdo Aug 05 '21 at 05:23

score 1 · Answer 4 · answered Sep 16 '11 at 10:53

It means OR

for example:

if this || that

means "if this or that"

So when the computer comes to the "||" part of your code, if the statement before it is true, it will stop reading that if statement and automatically execute the code underneath.

If the item before that "||" is false, then it will check the next one, and so on...

what does the "||" in a var statement mean?

4 Answers4