Array Buffer -> String and String -> ArrayBuffer conversions in javascript

arrayBufferToString.js

// source: http://stackoverflow.com/a/11058858
function ab2str(buf) {
  return String.fromCharCode.apply(null, new Uint16Array(buf));
}

stringToArrayBuffer.js

// source: http://stackoverflow.com/a/11058858
function str2ab(str) {
  var buf = new ArrayBuffer(str.length * 2); // 2 bytes for each char
  var bufView = new Uint16Array(buf);
  for (var i = 0, strLen = str.length; i < strLen; i++) {
    bufView[i] = str.charCodeAt(i);
  }
  return buf;
}

good!

Good, but typescript complains that new Uint16Array(buf) cannot be converted to number[].

Good, but typescript complains that new Uint16Array(buf) cannot be converted to number[].

Use this code to convert an array buffer to a number

convertArrayBufferToNumber(buffer: ArrayBuffer){
  const bytes = new Uint8Array(buffer);
  const dv = new DataView(bytes.buffer);
  return dv.getUint16(0, true);
}

Very good! Had to change the Uint16Array to Uint8Array and worked like a charm!

Use this code to convert an array buffer to a number

You can cast the Uint8Array (or any other ArrayBufferView) to number[] - it's working fine in my case -

Why does it need to be Uint16Array ? What 's the cost of instantiating another ArrayBufferView ? is it minimal right ? I my case I work both with binary and text files and I read both using Uint8Array and this method works fine just passing it directly and in TypeScript I must cast to any:

const s = String.fromCharCode.apply(null, anArrayBufferView as any)

I just posted a TS conversion of this: https://gist.github.com/AndrewLeedham/a7f41ac6bb678f1eb21baf523aa71fd5 feel free to use it. I used Array.from to convert the Uint16Array to a number[]. Casting will also work if you don't want the extra operation.

    const byteArrayStringA = String.fromCharCode.apply(null, Array.from(new Uint8Array(anArrayBufferA)));

const byteArrayString = String.fromCharCode.apply(null, Array.from(new Uint8Array(anArrayBufferB)));

      const byteArrayString = String.fromCharCode.apply(null, Array.from(new Uint8Array(anArrayBufferC)));

The above code giving me "Maximum call stack size exceeded" error.
Please help

I am getting this error when i execute above code:

multipart.ts:33:30 - error TS2339: Property 'charCodeAt' does not exist on type 'any[]'.

33 bufView[i] = post_data.charCodeAt(i);
~~~~~~~~~~

Try using:

function str2ab(text) {
    return new TextEncoder().encode(text);
}

@erycson - nice! It looks like TextEncoder/TextDecoder is now a global in node (as of v11.0.0). It was added in the util lib in v8.3.0.

Following your example. the ab2str function can be rewritten:

function ab2str(buf) {
  return new TextDecoder().decode(buf);
}

Very good! Had to change the Uint16Array to Uint8Array and worked like a charm!

Thanks! worked