Javascript array value is undefined ... how do I test for that

Posted by Ankur on Stack Overflow See other posts from Stack Overflow or by Ankur
Published on 2010-04-20T06:50:48Z Indexed on 2010/04/20 6:53 UTC
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Filed under:

JavaScript

|

arrays

|

undefined

I am trying to test to see whether a Javascript variable is undefined.

You will see that I am not expecting the value of predQuery[preId] to be 'undefined' if I don't first get an alert saying "its unbelievable". But I often do, so I am guessing that my statement

 predQuery[preId]=='undefined')

is not matching the undefined elements properly.

if((predQuery.length < preId) || (predQuery[preId]=="") || (predQuery[preId]=='undefined')){
alert("its unbelievable");
alert(predQuery[preId]);
queryPreds[variables] = preId;
queryObjs[variables] = objId;
predQuery[preId] = variables;
}
else {
    alert(predQuery[preId]);
var predIndex = predQuery[preId];
queryPreds[predIndex] = preId;
queryObjs[predIndex] = objId;
}

I can add more code if needed.

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