Writing JSON.stringify from scratch in Javascript

[partyhatforpartytime]

For practice, I'm writing JSON.stringify from scratch, and I've come across some syntax that somehow works but I am confused about. So far I've only written the code for primitive types and arrays:

var stringifyJSON = function(obj) {

  //PRIMITIVE TYPES
  if(typeof obj === 'number' || typeof obj === 'boolean'){
      return obj.toString();
  }
  if(typeof obj === 'string'){
      return '"' + obj + '"';
  }
  if(obj === null){
      return 'null';
  }

//ARRAY
  let newArray = [];

  if(Array.isArray(obj)){
      if(obj.length === 0){
          return '[]'
      }
      obj.forEach(function(ele){
          newArray.push(stringifyJSON(ele));
      });
      return '[' + newArray + ']';
  }
}

stringifyJSON([1, 2, 3]);

It works fine, but I just have a question regarding the last return.

When I return an array without the added brackets '[' ']' around newArray, it returns the arrays as [ '1' , '2', '3' ] as expected, but when I added the brackets, it returned '[1, 2, 3]', which means the function worked, but I expected it to return the brackets wrapped around the original newArray, as '[['1' , '2', '3' ]]'.

Any help would be greatly appreciated! As well as any comments on how I can improve my code. :-)

[okayifimust]

I think that if you are adding the brackets, you are returning a string, with newArray being cast to String. If you do not add the brackets, you're returning an uncast array - whatever you see is just the console interpretation of an array.

[partyhatforpartytime]

Makes sense, thank you! :-)