demo/typescript.js
function peekUnicodeEscape() {
            if (pos + 5 < end && text.charCodeAt(pos + 1) === 117 /* u */) {
                var start_1 = pos;
                pos += 2;
                var value = scanExactNumberOfHexDigits(4);
                pos = start_1;
                return value;
            }
            return -1;
        }
function peekUnicodeEscape() {
            if (pos + 5 < end && text.charCodeAt(pos + 1) === 117 /* u */) {
                var start_1 = pos;
                pos += 2;
                var value = scanExactNumberOfHexDigits(4);
                pos = start_1;
                return value;
            }
            return -1;
        }
Current character is known to be a backslash. Check for Unicode escape of the form '\uXXXX' and return code point value if valid Unicode escape is found. Otherwise return -1.