题解 | #计时器#

function count(start, end) {
    console.log(start)
    var timer = setInterval(() => {
        if  (start < end) {
            start ++
            console.log(start)
        } else {
            clearInterval(timer)
        }
        
    }, 100)
    return {
        cancel: function() {
            clearInterval(timer)
        }
    }
}