一把双刃剑：Scratch数据类型的隐式转换

_setCostume (target, requestedCostume, optZeroIndex) {
        if (typeof requestedCostume === 'number') {
            // Numbers should be treated as costume indices, always
            target.setCostume(optZeroIndex ? requestedCostume : requestedCostume - 1);
        } else {
            // Strings should be treated as costume names, where possible
            const costumeIndex = target.getCostumeIndexByName(requestedCostume.toString());

if (costumeIndex !== -1) {
                target.setCostume(costumeIndex);
            } else if (requestedCostume === 'next costume') {
                target.setCostume(target.currentCostume + 1);
            } else if (requestedCostume === 'previous costume') {
                target.setCostume(target.currentCostume - 1);
            // Try to cast the string to a number (and treat it as a costume index)
            // Pure whitespace should not be treated as a number
            // Note: isNaN will cast the string to a number before checking if it's NaN
            } else if (!(isNaN(requestedCostume) || Cast.isWhiteSpace(requestedCostume))) {
                target.setCostume(optZeroIndex ? Number(requestedCostume) : Number(requestedCostume) - 1);
            }

if (typeof index !== 'number') {
            if (index === 'all') {
                return acceptAll ? Cast.LIST_ALL : Cast.LIST_INVALID;
            }
            if (index === 'last') {
                if (length > 0) {
                    return length;
                }
                return Cast.LIST_INVALID;
            } else if (index === 'random' || index === 'any') {
                if (length > 0) {
                    return 1 + Math.floor(Math.random() * length);
                }
                return Cast.LIST_INVALID;
            }
        }

static toNumber (value) {
        // If value is already a number we don't need to coerce it with
        // Number().
        if (typeof value === 'number') {
            // Scratch treats NaN as 0, when needed as a number.
            // E.g., 0 + NaN -> 0.
            if (Number.isNaN(value)) {
                return 0;
            }
            return value;