check that a collection is not empty

How do you check that data.results in the following is not empty before trying to perform actions on it?

$.getJSON(myurl, function(data) {
  // if开发者_StackOverflow中文版 data.results is not empty 
  // {
  //    console.log(data.results.size);
  // }

});

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if (data != null && data.results != null && data.results.length > 0) {
    // the array is not empty
}

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I usually use something like this:

if (data != null && data.results != null && data.results.size != 0) ...

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how about doing this one?

if(data!=undefined){
// do logic here
}