javascript: How do I convert Uint8Array data to a JS object

Question

I am new to both Javascript and JSON worlds. I am wondering how I could convert an incoming Uint8Array data () to a JS object? Any help / pointers please. Here's what I have done as an experiment.

// arr is uint8Array incoming data
function myConvertFunc(arr) {
  let str = "";
  for (var i=0; i<arr.byteLength; i++) {
    str += String.fromCharCode(arr[i]);
  }

  // Say, 'str' at this step looks like below :
  /* {"type": "newEvent", "content": {"rec": [{"id1": "1", "event": "3A=","payload": "EZm9ydW0ub="}]}} */

  var serializedData = JSON.stringify(str);
  let message = JSON.parse(serializedData);

  switch (message.type) {
    case "newEvent":
      log("In newEvent");
      break;
     .
     .
     .
    default:
      log("undefined message type");
  }
}

Contrary to my understanding, the default case log : "undefined message type" is show in my logs. Could someone please help me figure out my mistake here?

The Uint8Array type represents an array of 8-bit unsigned integers. Not sure if this is the answer you are looking for — Siddartha
– Siddartha, Commented May 24, 2013 at 0:04
@MattBall: It's a typed array. See developer.mozilla.org/en-US/docs/JavaScript/Typed_arrays/… — Bergi
– Bergi, Commented May 24, 2013 at 0:13
@Siddartha: Why do you need to put a JSON string into a typed array (or the other way round)? — Bergi
– Bergi, Commented May 24, 2013 at 0:14

Bergi · Accepted Answer · 2013-05-24 00:19:33Z

5

var serializedData = JSON.stringify(str);
let message = JSON.parse(serializedData);

That means if there are no errors that str === serializedData (or at least two equal-looking objects).

Say, 'str' at this step looks like below:

{"type": "newEvent", "content": {"rec": [{"id1": "1", "event": "3A=","payload": "EZm9ydW0ub="}]}}

Now, if str is the JSON string then you just want

var message = JSON.parse(str);

Currently, you did JSON-encode and then -decode the JSON string, with the result that message was the string again and its type property was undefined.

answered May 24, 2013 at 0:19

Bergi

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3 Comments

Siddartha Over a year ago

Well, this is what I have tried at the very beginning. When I JSON.parse(str), I get the error : "JSON.parse: unexpected non-whitespace character after JSON data". Hence unsure of this error, resorted to the code snippet that I first posted. But thanks though for clarifying.

Bergi Over a year ago

Then probably your JSON string got amended with some invalid characters. Do a console.log(str) to make sure it is valid - not sure where you got your uint8array from and what else it might contain.

Siddartha Over a year ago

Thanks for identifying the issue. Indeed there was an extra character that was putting off JSON.parse(...). Now the issue is fixed. Appreciate your time.

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