Looping though unique keys

I have a json object which I would like to loop through; however each object has a nested object which I can't access through dot notation due to the values being unique.

.__proto__

will give me consistent results; however I'd like to pull out the values starting with the "-Jg". Is it possible to do this through a regular expression or another method?

Edit:

I'm looping through the 'javascript object' with angular

var lognew = [];

angular.forEach(log, function(value, key) {    
if(value){
  if(value.substr(0,3) !== "-Jg" ){    
  this.push(value);
   }
  }
}, lognew); 

console.log(lognew);

This currently returns:

 TypeError: undefined is not a function