undefined var can't be detected in Chrome console?

Question

I have read two full threads on this topic and tried all available syntaxes liste from both of them, and the variable is still undetected.

var undefined = false; if ( numLikes == undefined)

It's on this website: http://www.solidzapps.com/

If you use this script on the page, you will be able to find undefined likes, on many results:

$("#pageResults li").each(function (){ var viewsText = $(this).find(".duration-viewCount").text(); var numViews = +viewsText.match(/\|\s([^ ]+)/)[1].replace(/,/g, ""); var likesText = $(this).find(".likes").text(); var numLikes = +likesText.match("^([^ ]+)")[1].replace(/,/g, ""); //i think numlikes * 80 > numViews is what you're looking for, change that if not if (numLikes < 18 || numLikes * (25 + Math.min(15,numLikes/5)) + Math.min(30,numLikes/18) < numViews) { $(this).css("height", "0"); } var undefined = false; if ( numLikes == undefined) { $(this).css("height", "0"); } });

var undefined = false; if ( numLikes == undefined) makes no sense... What are you trying to accomplish with this part of the script? — Andreas
– Andreas, Commented Feb 25, 2017 at 11:40
Andreas, That makes no sense because it's unofficial, it's an alledgedly working coding trick. i took it from an answer that had about 20 up votes, from a page nearly the same as my question. It's a trick i found from the 2nd/3rd most popular answer for dealing with undefined vars, it had at least 20 votes. — bandybabboon
– bandybabboon, Commented Feb 25, 2017 at 14:11
Siam, I thought that your code worked at first, however, it selects every instance of the identifier, whether it is an integer or an undefined value, so in effect it doesnt work at all. — bandybabboon
– bandybabboon, Commented Feb 25, 2017 at 15:24
numLikes will never be undefined nor false. Also you cannot overwrite undefined. — Andreas
– Andreas, Commented Feb 25, 2017 at 17:19

sanket · Accepted Answer · 2017-02-26 12:19:10Z

1

In the example you have provided, numLikes comes out to be 'NaN' attributed to this line in your code var numLikes = +likesText.match("^([^ ]+)")[1].replace(/,/g, "");

Try this:

if(isNaN(numLikes)) { //do Something }

or

if(!numLikes) { // do Something }

My previous answer didn't work because typeof NaN is number not undefined

edited Feb 26, 2017 at 12:19

answered Feb 25, 2017 at 11:48

sanket

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5 Comments

Andreas Over a year ago

numLikes will never be undefined

bandybabboon Over a year ago

it doesnt work for this question, I had tried that already because i read 20 answers for coping with undefined values in other pages. nothing works for undefined on the solidzapps website for number of likes.

sanket Over a year ago

I can't get the case where 'numLikes' is undefined. Even when no search is performed there are no DOM nodes with selector as "#pageResults li".

bandybabboon Over a year ago

Hey thanks, I added an example to the top of the page. I just typed acid jazz downtempo, set it to 50 results, and have two undefined results.

bandybabboon Over a year ago

I want to say Thanks a lot! it's awesome, the isNaN version is working thank you.

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