GLib.utf8_strlen

function utf8_strlen(p: String, max: Number(gssize)): Number(glong) {
    // Gjs wrapper for g_utf8_strlen()
}

Computes the length of the string in characters, not including the terminating nul character. If the max'th byte falls in the middle of a character, the last (partial) character is not counted.

p: pointer to the start of a UTF-8 encoded string
max: the maximum number of bytes to examine. If max is less than 0, then the string is assumed to be nul-terminated. If max is 0, p will not be examined and may be null. If max is greater than 0, up to max bytes are examined
Returns: the length of the string in characters