Get a promise which resolves once a given function returns true. The promise will set an interval and poll the function at a specified interval until it becomes true.

PollingPromise.js

// Resolves once the check function returns true
// You optionally specify the interval at which to poll the check function. Default = 1000ms

// TODO: add timeout functionality

class PollingPromise extends Promise {
    constructor(check, interval = 1000){
        super(resolve => {
            if(this.check()){ return resolve() }
            const interval = setInterval(async () => {
                if(this.check()){
                    clearInterval(interval)
                    return resolve()
                }
            }, interval)
        })
    }
}
PollingPromise.prototype.constructor = Promise

/* Example usage:

class MyClass {
    constructor(){
        // after you set this._isReady to true, promises returned from .ready will resolve
        this._isReady = false
    }
    get ready(){
        return this._isReady? Promise.resolve() : new PollingPromise(() => this._isReady, 250)
    }
}

*/