为什么我的if...else 语句， else不能执行？

Question

    <div class="box" id="box"></div>

    <button onclick="myfunction()">按钮</button>

    <script>

    function myfunction() {

    var box = document.getElementById("box");

        if (box.style.backgroundColor="aqua") 

            {

                box.style.backgroundColor="red";

            }

        else {

            box.style.backgroundColor="black";

        }

    }

    </script>

Answer 1

详情见图片

Answer 2

f (box.style.backgroundColor="aqua") 改为f (box.style.backgroundColor=="aqua") ，你写的是个赋值语句，双等或恒等（3个等号）才是判断语句

Answer 3

= == === 的区别可以看一下

Answer 4

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

Answer 5

你看下你的判断语句==

Answer 6

box.style.backgroundColor="aqua"，一个“=”是赋值符号，用“==”或者“===”才是判断是否相等的符号。你改成box.style.backgroundColor==="aqua"试试