in scripts/build.js [571:589]
function toCodePoint(unicodeSurrogates, sep) {
var
r = [],
c = 0,
p = 0,
i = 0;
while (i < unicodeSurrogates.length) {
c = unicodeSurrogates.charCodeAt(i++);
if (p) {
r.push((0x10000 + ((p - 0xD800) << 10) + (c - 0xDC00)).toString(16));
p = 0;
} else if (0xD800 <= c && c <= 0xDBFF) {
p = c;
} else {
r.push(c.toString(16));
}
}
return r.join(sep || '-');
}