Babylon.js/src/Tools/deferred.ts

    /**
     * Wrapper class for promise with external resolve and reject.
     */
    export class Deferred<T> {
        /**
         * The promise associated with this deferred object.
         */
        public readonly promise: Promise<T>;

        private _resolve: (value?: T | PromiseLike<T>) => void;
        private _reject: (reason?: any) => void;

        /**
         * The resolve method of the promise associated with this deferred object.
         */
        public get resolve() {
            return this._resolve;
        }

        /**
         * The reject method of the promise associated with this deferred object.
         */
        public get reject() {
            return this._reject;
        }

        /**
         * Constructor for this deferred object.
         */
        constructor()
        {
            this.promise = new Promise((resolve, reject) => {
                this._resolve = resolve;
                this._reject = reject;
            });
        }
    }