解决将变量更改为一定值的承诺

Question

我正在使用reactivex和typescript编写一个控制充电电池的应用程序。我在这里使用了很多promise，这使我想到了一个问题：我希望链中的promise只要变量（收费状态）达到一定值就可以解决。

我尝试使用while循环来定期检查该值，并在达到该值后立即返回，但这会阻塞整个程序。

private _performChargeJob(job: ChargeJob): Promise<any> {
    // Return a promise that is resolved if the job has finished processing.
    return this._performGoal(job.goals[0].goalId)
        .then(() => {
            this._handleCharge(this._soc, 100); // this is the important part where I'd wish the promise to resolve
        }).then(() => {
            this.logConsole("Finished charging.");
            this.callRosService({name: "set_charge_state", serviceType: "insystems_srvs/SetChargeState"}, {
                set_charge_state: 0,                 // stop charging
            });
        });
}

private _handleCharge(soc: number, maxSoc: number) {
// this function should return/resolve a promise when variable soc reaches 100.0
    this.logConsole("starting charge.");
    this.callRosService({name: "set_charge_state", serviceType: "insystems_srvs/SetChargeState"}, {
        set_charge_state: 1,                // start charging
    });
}

在这里，我期望某种watch()（已过时）或新的promise可以等待该值达到该水平。甚至可能是observable？

谢谢！