SOURCE

class ZephyrCountdown {
    constructor(targetDate) {
        this.targetTime = new Date(targetDate).getTime()
        this.intervalId = null
    }

    makeCountdown(res = Function) {
        const currTime = new Date().getTime()
        const leftTime = this.targetTime - currTime 

        if (leftTime <= 0) clearInterval(this.intervalId)

        const d = Math.floor(leftTime / (1000 * 60 * 60 * 24))
        const h = Math.floor((leftTime / (1000 * 60 * 60)) % 24)
        const m = Math.floor((leftTime / (1000 * 60)) % 60);
        const s = Math.floor((leftTime / 1000) % 60);
        const left = {d, h, m, s}
        res(left)
    }

    start(val = Function) {
        this.intervalId = setInterval(() => {
            this.makeCountdown( res => val(res))
        }, 1000)
    }

    stop() {
        clearInterval(this.intervalId)
    }
}


const counter = new ZephyrCountdown('2023-05-20 12:26:59')
counter.start( val => {
    console.log('val: ', val)
})

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