JS Script Returning Undefined Instead of Expected String

Question

I basically have been making a program that will go through a website and grab certain images. This is not too hard, just a little complex. I was running the JS code below to click onto the correct page, check for the gallery element to load every 100ms, then finally log the entire object as a string. Most works, but when getting the console.log(...); I get undefined as the main return, and I get the string afterwards as a secondary. This will not due because my program can only intercept the main logged value, not any secondaries. Below is my code and an example output. Thank you!

Code:

document.getElementById('tlcItem_47871').click();
var checkExist = setInterval(function() {
    if ($('.pgFooterThumblist').length) {
        clearInterval(checkExist);
        var ele = document.getElementsByClassName('pgFooterThumb');
        console.log(JSON.stringify(ele));
    }
}, 100);

Ex Output:

/*Primary Output(First)*/<- undefined
/*Secondary Output(Second)*/<- {"0":{},"1":{},"2":{},"3":{},"4":{},"5":{},"6":{},"7":{},"8":{},"9":{},"10":{},"11":{},"12":{},"13":{},"14":{},"15":{},"16":{},"17":{},"18":{},"19":{},"20":{},"21":{},"22":{},"23":{},"24":{},"25":{},"26":{},"27":{},"28":{},"29":{},"30":{},"31":{},"32":{},"33":{},"34":{},"35":{},"36":{},"37":{},"38":{},"39":{},"40":{},"41":{},"42":{},"43":{},"44":{},"45":{},"46":{},"47":{},"48":{},"49":{},"50":{},"51":{},"52":{},"53":{},"54":{},"55":{},"56":{},"57":{},"58":{},"59":{},"60":{},"61":{},"62":{},"63":{},"64":{},"65":{},"66":{},"67":{},"68":{},"69":{},"70":{},"71":{},"72":{},"73":{},"74":{},"75":{},"76":{},"77":{},"78":{},"79":{},"80":{},"81":{},"82":{},"83":{},"84":{},"85":{},"86":{},"87":{},"88":{},"89":{},"90":{},"91":{},"92":{},"93":{},"94":{},"95":{},"96":{},"97":{},"98":{},"99":{},"100":{},"101":{},"102":{},"103":{},"104":{},"105":{},"106":{},"107":{},"108":{},"109":{},"110":{},"111":{},"112":{},"113":{},"114":{},"115":{},"116":{},"117":{},"118":{},"119":{},"120":{},"121":{},"122":{},"123":{},"124":{},"125":{},"126":{},"127":{},"128":{},"129":{},"130":{},"131":{},"132":{},"133":{},"134":{},"135":{},"136":{},"137":{},"138":{},"139":{},"140":{},"141":{},"142":{},"143":{},"144":{},"145":{},"146":{},"147":{},"148":{},"149":{},"150":{},"151":{},"152":{},"153":{},"154":{},"155":{},"156":{},"157":{},"158":{},"159":{},"160":{},"161":{},"162":{},"163":{},"164":{},"165":{},"166":{},"167":{},"168":{},"169":{},"170":{},"171":{},"172":{},"173":{},"174":{},"175":{},"176":{},"177":{},"178":{},"179":{},"180":{},"181":{},"182":{},"183":{},"184":{},"185":{},"186":{},"187":{},"188":{},"189":{},"190":{},"191":{},"192":{},"193":{},"194":{},"195":{},"196":{},"197":{},"198":{},"199":{},"200":{},"201":{},"202":{},"203":{},"204":{},"205":{},"206":{},"207":{},"208":{},"209":{},"210":{},"211":{},"212":{},"213":{},"214":{},"215":{},"216":{},"217":{},"218":{},"219":{}}

EDIT: In the workflow that I have I am able to set my JS script in my c++, and then I can run javascript into a loaded webpage. The only issue is that the runJavascript() function will take the first value outputted and use that. No way around it so I need the string to be outputted ASAP.

I assume you're entering this into the console? It's normal for a command to return undefined. — E. Sundin
– E. Sundin, Commented Mar 21, 2017 at 3:40
I feel like I don't fully understand your issue-- you just need it to not console log for undefined values? What is required? — Alexander Nied
– Alexander Nied, Commented Mar 21, 2017 at 3:40
@JaromandaX This is the output that i see first in the console & the one my program interprets. — Nicholas Johnson
– Nicholas Johnson, Commented Mar 21, 2017 at 3:40
@NicholasJohnson var a = "a" also returns undefined. Why would you want that though? The undefined return isn't a problem in itself, if it's a problem for you then specify why that is. — E. Sundin
– E. Sundin, Commented Mar 21, 2017 at 3:43

Alexander Nied · Accepted Answer · 2017-03-21 04:01:24Z

1

THIS IS NOT A CORRECT ANSWER. I AM LEAVING IT FOR CONTEXT ONLY.

Assuming that all that is need is to avoid console logging an undefined value, this would suffice:

document.getElementById('tlcItem_47871').click();
var checkExist = setInterval(function() {
    if ($('.pgFooterThumblist').length) {
        clearInterval(checkExist);
        var ele = document.getElementsByClassName('pgFooterThumb');
        var loggedOutput = JSON.stringify(ele);
        if (loggedOutput) {
            console.log(loggedOutput);
        }
    }
}, 100);

This is assuming that somehow your C code intercepts this console log. Generally in JavaScript if you need a value from a function you need to pass it back to the caller using a return statement, but it seems that perhaps you have a unique case in which this is not required.

edited Mar 21, 2017 at 4:01

answered Mar 21, 2017 at 3:57

Alexander Nied

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3 Comments

Nicholas Johnson Over a year ago

Just tested, first value logged is still undefined

Alexander Nied Over a year ago

OK, then this is not the answer for you-- there may be more going on under the hood here than meets the eye.

Nicholas Johnson Over a year ago

Thank you very mush for trying!

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