SillyTavern/src/polyfill.js

if (!Array.prototype.findLastIndex) {
    Array.prototype.findLastIndex = function (callback, thisArg) {
        for (let i = this.length - 1; i >= 0; i--) {
            if (callback.call(thisArg, this[i], i, this)) return i;
        }
        return -1;
    };
}

module.exports = {};