UTF-8 to UTF-16LE Javascript

Question

I need to convert an utf-8 string to utf-16LE in javascript like the iconv() php function.

Ie:

iconv("UTF-8", "UTF-16LE", $string);

The output should be like this:

49 00 6e 00 64 00 65 00 78 00

I found this func to decode UTF-16LE and it's works fine but i don't know how to do the same to encode.

function decodeUTF16LE( binaryStr ) {
    var cp = [];
    for( var i = 0; i < binaryStr.length; i+=2) {
        cp.push( 
             binaryStr.charCodeAt(i) |
            ( binaryStr.charCodeAt(i+1) << 8 )
        );
    }

    return String.fromCharCode.apply( String, cp );
}

The conclusion is to create a binary file that can be downloaded.

The code:

function download(filename, text) {
    var a = window.document.createElement('a');

    var byteArray = new Uint8Array(text.length);
    for (var i = 0; i < text.length; i++) {
        byteArray[i] = text.charCodeAt(i) & 0xff;
    }
    a.href = window.URL.createObjectURL(new Blob([byteArray.buffer], {'type': 'application/type'}));

    a.download = filename;

    // Append anchor to body.
    document.body.appendChild(a);
    a.click();

    // Remove anchor from body
    document.body.removeChild(a);
}

Answer 1

Thanks a lot Bergi, this works perfectly combining to standard utf8 to utf16 encode function:

function encodeUTF16LE(str) {
    var out, i, len, c;
    var char2, char3;

    out = "";
    len = str.length;
    i = 0;
    while(i < len) {
        c = str.charCodeAt(i++);
        switch(c >> 4)
        { 
          case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
            // 0xxxxxxx
            out += str.charAt(i-1);
            break;
          case 12: case 13:
            // 110x xxxx   10xx xxxx
            char2 = str.charCodeAt(i++);
            out += String.fromCharCode(((c & 0x1F) << 6) | (char2 & 0x3F));
            out += str.charAt(i-1);
            break;
          case 14:
            // 1110 xxxx  10xx xxxx  10xx xxxx
            char2 = str.charCodeAt(i++);
            char3 = str.charCodeAt(i++);
            out += String.fromCharCode(((c & 0x0F) << 12) | ((char2 & 0x3F) << 6) | ((char3 & 0x3F) << 0));
            break;
        }
    }

    var byteArray = new Uint8Array(out.length * 2);
    for (var i = 0; i < out.length; i++) {
        byteArray[i*2] = out.charCodeAt(i); // & 0xff;
        byteArray[i*2+1] = out.charCodeAt(i) >> 8; // & 0xff;
    }

    return String.fromCharCode.apply( String, byteArray );
}

Answer 2

This should do it:

var byteArray = new Uint8Array(text.length * 2);
for (var i = 0; i < text.length; i++) {
    byteArray[i*2] = text.charCodeAt(i) // & 0xff;
    byteArray[i*2+1] = text.charCodeAt(i) >> 8 // & 0xff;
}

It's the inverse of your decodeUTF16LE function. Notice that neither works with code points outside of the BMP.