Function ucs2decode

lib/punycode.js:113–135

* Creates an array containing the numeric code points of each Unicode * character in the string. While JavaScript uses UCS-2 internally, * this function will convert a pair of surrogate halves (each of which * UCS-2 exposes as separate characters) into a single code point, * matching UTF-16. *

(string)

 * @returns {Array} The new array of code points.
 */
function ucs2decode(string) {
	const output = [];
	let counter = 0;
	const length = string.length;
	while (counter < length) {
		const value = string.charCodeAt(counter++);
		if (value >= 0xD800 && value <= 0xDBFF && counter < length) {
			// It's a high surrogate, and there is a next character.
			const extra = string.charCodeAt(counter++);
			if ((extra & 0xFC00) == 0xDC00) { // Low surrogate.
				output.push(((value & 0x3FF) << 10) + (extra & 0x3FF) + 0x10000);
			} else {
				// It's an unmatched surrogate; only append this code unit, in case the
				// next code unit is the high surrogate of a surrogate pair.
				output.push(value);
				counter--;
			}
		} else {
			output.push(value);
		}
	}
	return output;
}

/**
 * Creates a string based on an array of numeric code points.