Considering text as an array variable, please explain the push method statement shown below:
var text = [];
text.push(document.getElementById('name').innerHTML || 0);
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j08691
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user1934643
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1Add the innerHTML string or 0 to the end of the array ... – adrian Jan 18 '13 at 19:48
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What do you need explained? Did you try it in the developer console? – zzzzBov Jan 18 '13 at 19:48
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Copy-pasted exam question? – John Dvorak Jan 18 '13 at 19:50
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I am new to JavaScript and my confusion is only with '|| 0' part in that statement. I mean what is the purpose of adding this part along with document.getElementById('name').innerHTML? – user1934643 Jan 18 '13 at 19:52
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@Jan: No, it's not copy pasted. Actually I was studying some script and come across such a statement. As I said, I am new to JS and have seen push method with only one value so far.... – user1934643 Jan 18 '13 at 19:54
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2Duplicate of http://stackoverflow.com/questions/2802055/what-does-this-construct-x-x-y-mean – Felix Kling Jan 18 '13 at 19:57
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@user1934643 your code is also about pushing ONE value. – zs2020 Jan 18 '13 at 19:58
2 Answers
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The trick is that an empty string is evaluated as false in boolean tests like this.
Example :
var a = "" || 0; // a is set to 0 because "" is empty and is false
var b = "non-empty" || 0 // b is set to "non-empty" because it's not an empty string
Mike Park
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Thank so much climbage, though I was also guessing the same but was doubtful so wanted to get it confirmed with experts as I have never seen such an expression before....Once again a big thanks to you for making me clear on this :-) – user1934643 Jan 18 '13 at 20:02
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@user1934643 Okay, I kinda regret my close vote now (too late, I know). Just FYI, this kind of use of `||` is called "short-circuit boolean evaluation". See the question linked as possible duplicate in the comments above. – bfavaretto Jan 18 '13 at 20:05
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@bfavaretto it's never too late to retract a close vote. We have a thing called "reopen votes". However, if this gets reopened, the next step will be to close this as a duplicate. – John Dvorak Jan 18 '13 at 20:06
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@JanDvorak In this particular case, I regret the close vote *reason* (I'd prefer "dupe", but couldn't find a good one and voted for "too localized"). So I won't vote to reopen just to have it closed again. – bfavaretto Jan 18 '13 at 20:08
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it will add HTML content of dom element with id='name' if it's not empty to text array , otherwise it will add 0 to it
Basemm
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