如何从另一个函数访问一个函数中的变量？

Question

如何从另一个称为“ STOP”的函数访问变量“ count_down”，以便可以“ clearInterval（count_down）”。

代码

    function START(){
        let count_down = setInterval(countDown, 1000);
        up.setAttribute("disabled" , true)
        down.setAttribute("disabled" , true)
        count.innerHTML = "stop";
        return count_down;
    }


    function STOP(){
        clearInterval(count_down)
        up.removeAttribute("disabled");
        down.removeAttribute("disabled");
        count.innerHTML = "start";
    }

故障排除：

Uncaught ReferenceError: count_down is not defined
    at STOP (main.js:112)
    at HTMLButtonElement.count.onclick (main.js:123)

Answer 1

您可以执行以下操作。

let count_down=0;

function START(){
        count_down = setInterval(countDown, 1000);
        up.setAttribute("disabled" , true)
        down.setAttribute("disabled" , true)
        count.innerHTML = "stop";
        return count_down;
    }


    function STOP(){
        clearInterval(count_down)
        up.removeAttribute("disabled");
        down.removeAttribute("disabled");
        count.innerHTML = "start";
    }