The JavaScript method String.fromCharCode() behaves equivalently to Python's unichar() in the following sense:

print unichr(213) # prints Õ on the console 
console.log(String.fromCharCode(213)); // prints Õ on the console as well

For my purposes, however, I need a JavaScript equivalent to the Python function chr(). Is there such a JavaScript function or a way to make String.fromCharCode() behave like chr()?

That is, I need something in JavaScript that mimics

print chr(213) # prints � on the console

The JavaScript method String.fromCharCode() behaves equivalently to Python's unichar() in the following sense:

print unichr(213) # prints Õ on the console 
console.log(String.fromCharCode(213)); // prints Õ on the console as well

For my purposes, however, I need a JavaScript equivalent to the Python function chr(). Is there such a JavaScript function or a way to make String.fromCharCode() behave like chr()?

That is, I need something in JavaScript that mimics

print chr(213) # prints � on the console

• javascript
• python
• node.js
• fromcharcode

• 3 You should add more explanation of what you are trying to do and how String.fromCharCode is not doing it for you. If you merely want to show the unicode replacement character in console, you can do String.fromCharCode(0xFFFD) – Esailija Commented Jul 29, 2012 at 10:31
• (As a side note, you shouldn't be doing print unichr(stuff).) – Julian Commented Jul 29, 2012 at 16:24

2 Answers 2

So turns out you just want to work with raw bytes in node.js, there's a module for that. If you are a real wizard, you can get this stuff to work with javascript strings alone but it's harder and far less efficient.

var b = new Buffer(1);
b[0] = 213;

console.log(b.toString()); //�


var b = new Buffer(3);
b[0] = 0xE2;
b[1] = 0x98;
b[2] = 0x85;

console.log(b.toString()); //★

print chr(213) # prints � on the console

So this prints a raw byte (0xD5), that is interpreted in UTF-8 (most likely) which is not valid UTF-8 byte sequence and thus is displayed as the replacement character (�).

The interpretation as UTF-8 is not relevant here, you most likely just want raw bytes.

To create raw bytes in javascript you could use UInt8Array.

var a = new Uint8Array(1);
a[0] = 213;

You could optionally then interpret the raw bytes as utf-8:

console.log( utf8decode(a)); // "�"

//Not remended for production use ;D
//Doesn't handle > BMP to keep the answer shorter
function utf8decode(uint8array) {
    var codePoints = [],
        i = 0,
        byte, codePoint, len = uint8array.length;
    for (i = 0; i < len; ++i) {
        byte = uint8array[i];

        if ((byte & 0xF8) === 0xF0 && len > i + 3) {

            codePoint = ((byte & 0x7) << 18) | ((uint8array[++i] & 0x3F) << 12) | ((uint8array[++i] & 0x3F) << 6) | (uint8array[++i] & 0x3F);
            if (!(0xFFFF < codePoint && codePoint <= 0x10FFFF)) {
                codePoints.push(0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD);
            } else {
                codePoints.push(codePoint);
            }
        } else if ((byte & 0xF0) === 0xE0 && len > i + 2) {

            codePoint = ((byte & 0xF) << 12) | ((uint8array[++i] & 0x3F) << 6) | (uint8array[++i] & 0x3F);
            if (!(0x7FF < codePoint && codePoint <= 0xFFFF)) {
                codePoints.push(0xFFFD, 0xFFFD, 0xFFFD);
            } else {
                codePoints.push(codePoint);
            }
        } else if ((byte & 0xE0) === 0xC0  && len > i + 1) {

            codePoint = ((byte & 0x1F) << 6) | ((uint8array[++i] & 0x3F));
            if (!(0x7F < codePoint && codePoint <= 0x7FF)) {
                codePoints.push(0xFFFD, 0xFFFD);
            } else {
                codePoints.push(codePoint);
            }
        } else if ((byte & 0x80) === 0x00) {
            codePoints.push(byte & 0x7F);
        } else {
            codePoints.push(0xFFFD);
        }
    }
    return String.fromCharCode.apply(String, codePoints);
}

What you are most likely trying to do has nothing to do with trying to interpret the bytes as utf8 though.

Another example:

//UTF-8 For the black star U+2605 ★:
var a = new Uint8Array(3);
a[0] = 0xE2;
a[1] = 0x98;
a[2] = 0x85;
utf8decode(a) === String.fromCharCode(0x2605) //True
utf8decode(a) // ★

In python 2.7 (Ubuntu):

print chr(0xE2) + chr(0x98) + chr(0x85)
#prints ★

If you want this "Questionmark in a box" for every number that is not in the standard ASCII table, how about this little function?

function chr(c) {
    return (c < 0 || c > 126) ? '�' : String.fromCharCode(c);
}