json null check not working

I am doing the following null check , even thought the object is null its still unabl开发者_StackOverflow中文版e to check that

if(callbackResults.Details[0].Tags!='') // Tags are coming as null from backend..

details is a json object. Tags is again a object array inside details.

the above null check is failing and its going inside the loop

can you tell whats going wrong there.

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You can't test for null by comparison with an empty string. Try this:

 if (callbackResults.Details[0].Tags) {
   // not null
 }

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That is a check to see if Tags is an empty string. A check for 'not null' in JavaScript is this:

if(callbackResults.Details[0].Tags)

Note that this also checks for a booean 'true' condition, but this is the common way to make sure something is not null in javascript.

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Changing the if should do it, as described above. Else, if Tags is an array, you might check if the length is larger than zero:

if(callbackResults.Details[0].Tags.length > 0)