Function normalizeUrl

lib/css/CssParser.js:133–175

(str, isString)

 * @returns {string} normalized url
 */
const normalizeUrl = (str, isString) => {
	// Fast paths: skip the regex engine for the common URL with no escape and
	// no edge whitespace (e.g. `./img.png`). Each guard is equivalent to the
	// regex being a no-op.
	// Remove escaped newlines from a string-token url like `url("im\<newline>g.png")`.
	if (isString && str.includes("\\")) {
		str = str.replace(STRING_MULTILINE, "");
	}

	// Remove unnecessary spaces from `url("   img.png	 ")`
	if (
		str.length !== 0 &&
		(isCssWhitespace(str.charCodeAt(0)) ||
			isCssWhitespace(str.charCodeAt(str.length - 1)))
	) {
		str = str.replace(TRIM_WHITE_SPACES, "");
	}

	// Unescape
	if (str.includes("\\")) {
		str = str.replace(UNESCAPE, (match) => {
			if (match.length > 2) {
				return String.fromCharCode(Number.parseInt(match.slice(1).trim(), 16));
			}
			return match[1];
		});
	}

	if (/^data:/i.test(str)) {
		return str;
	}

	if (str.includes("%")) {
		// Convert `url('%2E/img.png')` -> `url('./img.png')`
		try {
			str = decodeURIComponent(str);
		} catch (_err) {
			// Ignore
		}
	}

	return str;
};

// `escapeIdentifier` / `unescapeIdentifier` live in ./syntax.js; they're re-exported at the bottom for back-compat callers.