how to push values from listObjects to an array

I have an array for example named yourArray. var yourArray = []; When I get object names with listObjects from s3, I want to push this object names to the array.

var params ={
     Bucket: 'exBucket',
     Prefix: 'somePrefix'
      };
s3.listObjects(params, function(Err, Data){
    if(!Err){
      for (var i = 0; i < Data.Contents.length; i++){
         console.log('Listed: ', Data.Contents[i].Key);
yourArray.push(Data.Contents[i].Key);
         }};
    });

Here, console.log('Listed: ', Data.Contents[i].Key); gives me the all names. But yourArray.push(Data.Contents[i].Key); doesnt push the names and array is still empty. Where is the mistake ?