A partially implemented A+ compliant Promise class

promise.js

// const GlobalPromise = global.Promise;

// delete global.Promise;

function typename(value) {
    if (typeof value == "object" && typeof value != "null") {
        let name;

        try {
            name = value.constructor?.name;
        } catch {}

        return name ? `#<${name}>` : Object.prototype.toString.call(value);
    } else {
        return String(value);
    }
}

class Promise {
    constructor(executor) {
        // this._value = null;
        // this._reason = null;

        // this._resolved = false;
        // this._rejected = false;

        // this._head = null;
        // this._tail = null;

        if (typeof executor != "function") {
            throw new TypeError(
                `Promise resolver ${typename(executor)} is not a function`
            );
        }

        try {
            executor(this._resolve.bind(this), this._reject.bind(this));
        } catch (reason) {
            this._reject(reason);
        }
    }

    //  [[Resolve]] - Promise Resolution Procedure
    _resolve(value) {
        if (this._resolved) {
            return;
        }

        if (this == value) {
            this._reject(new TypeError("Cyclic promise chain detected"));
        } else if (value instanceof Promise) {
            if (value._resolved) {
                if (value._rejected) {
                    this._reject(value._reason);
                } else {
                    this._resolve(value._reason);
                }
            } else {
                value.then(this._resolve.bind(this), this._reject.bind(this));
            }
        } else if (typeof value?.then == "function") {
            let then;

            try {
                then = value.then;
            } catch (err) {
                this._reject(err);
            }

            try {
                then.call(
                    value,
                    this._resolve.bind(this),
                    this._reject.bind(this)
                );
            } catch (err) {
                this._reject(err);
            }
        } else {
            this._fulfill(value);
        }
    }

    _fulfill(value) {
        this._value = value;
        this._resolved = true;
        this._rejected = false;

        while (this._head) {
            if (typeof this._head.onResolved == "function") {
                queueMicrotask(() => {
                    try {
                        this._head.resolve(this._head.onFulfilled(value));
                    } catch (err) {
                        this._head.reject(err);
                    }
                });
            }

            this._head = this._head.next;
        }
    }

    _reject(reason) {
        this._reason = reason;
        this._resolved = true;
        this._rejected = true;

        while (this._head) {
            if (typeof this._head.onRejected == "function") {
                queueMicrotask(() => {
                    try {
                        this._head.resolve(this._head.onRejected(reason));
                    } catch (err) {
                        this._head.reject(err);
                    }
                });
            }

            this._head = this._head.next;
        }
    }

    then(onFulfilled, onRejected) {
        let child;
        let promise = new Promise((resolve, reject) => {
            child = { resolve, reject, onFulfilled, onRejected };
        });

        this._tail = this._tail
            ? (this._tail.next = child)
            : (this._head = child);

        return promise;
    }

    catch(onRejected) {
        return this.then(undefined, onRejected);
    }

    finally(onFinally) {
        return this.then(
            (value) => (onFinally(), value),
            (value) => {
                onFinally();
                throw value;
            }
        );
    }

    static resolve(value) {
        return new Promise((resolve) => resolve(value));
    }

    static reject(reason) {
        return new Promise((_, reject) => reject(reason));
    }
}