To express, for example, the character U+10400 in JavaScript, I use uD801uDC00 or String.fromCharCode(0xD801) + String.fromCharCode(0xDC00). How do I figure that out for a given unicode character? I want the following:
var char = getUnicodeCharacter(0x10400);
How do I find 0xD801 and 0xDC00 from 0x10400?
Based on the wikipedia article given by Henning Makholm, the following function will return the correct character for a code point:
function getUnicodeCharacter(cp) {
if (cp >= 0 && cp <= 0xD7FF || cp >= 0xE000 && cp <= 0xFFFF) {
return String.fromCharCode(cp);
} else if (cp >= 0x10000 && cp <= 0x10FFFF) {
// we substract 0x10000 from cp to get a 20-bits number
// in the range 0..0xFFFF
cp -= 0x10000;
// we add 0xD800 to the number formed by the first 10 bits
// to give the first byte
var first = ((0xffc00 & cp) >> 10) + 0xD800
// we add 0xDC00 to the number formed by the low 10 bits
// to give the second byte
var second = (0x3ff & cp) + 0xDC00;
return String.fromCharCode(first) + String.fromCharCode(second);
}
}
