Function testRegExp

docs/app/js/sanddance-app.js:143873–143900

(pattern, flags)

    };
}
function testRegExp(pattern, flags) {
    let tmp = pattern;
    if (flags.indexOf("u") >= 0) // Replace each astral symbol and every Unicode code point
    // escape sequence with a single ASCII symbol to avoid throwing on
    // regular expressions that are only valid in combination with the
    // `/u` flag.
    // Note: replacing with the ASCII symbol `x` might cause false
    // negatives in unlikely scenarios. For example, `[\u{61}-b]` is a
    // perfectly valid pattern that is equivalent to `[a-b]`, but it
    // would be replaced by `[x-b]` which throws an error.
    tmp = tmp.replace(/\\u\{([0-9a-fA-F]+)\}/g, ($0, $1)=>{
        if (parseInt($1, 16) <= 0x10FFFF) return "x";
        throwError({}, MessageInvalidRegExp);
    }).replace(/[\uD800-\uDBFF][\uDC00-\uDFFF]/g, "x");
     // First, detect invalid regular expressions.
    try {
        new RegExp(tmp);
    } catch (e) {
        throwError({}, MessageInvalidRegExp);
    } // Return a regular expression object for this pattern-flag pair, or
    // `null` in case the current environment doesn't support the flags it
    // uses.
    try {
        return new RegExp(pattern, flags);
    } catch (exception) {
        return null;
    }
}
function scanRegExpBody() {
    var ch, str, classMarker, terminated, body;
    ch = source[index];