显示Uncaught TypeError: timer is not a function

var index = 0
        var imgs = document.getElementsByClassName("img")
        var box = document.querySelector(".box-img")
        var left = document.querySelector(".button-left")
        var right = document.querySelector(".button-right")
        function position() {
            box.style.left = (index * -100) + "%"
        }
        function timer() {
            time = setInterval(() => {
                index++
                add()
                desc()
                position()
            }, 3000)
        }
        function add() {
            if (index >= imgs.length - 1) {
                index = 0
            }
            else {
                index++
            }
        }
        function desc() {
            if (index < 1) {
                index = imgs.length - 1
            }
            else {
                index--
            }
        }
        left.addEventListener("click", () => {
            desc()
            position()
            clearInterval(time)
            timer()
        })
        right.addEventListener("click", () => {
            add()
            position()
            clearInterval(time)
            timer()
        })
        timer()

就是left和right两个按钮里面清除了计时器就不能够重新调用了

timer 不是一个函数。去掉 clearInterval可以运行吗？