求解：关于使用if与switch做相同判断时，判断结果不同的问题

Question

现象：使用if与switch做判断时，判断结果不同

```javascript
<script>
            document.addEventListener("keydown", (event) => {
                if (event.key === "ArrowUp" || "Up") {
                    console.log("if", event.key, "up");
                } else if (event.key === "ArrowDown" || "Down") {
                    console.log(event.key, "down");
                } else if (event.key === "ArrowLeft" || "Left") {
                    console.log(event.key, "left");
                } else if (event.key === "ArrowRight" || "Right") {
                    console.log(event.key, "right");
                }
                switch (event.key) {
                    case "ArrowUp" || "Up":
                        console.log("switch", event.key, "up");
                        break;
                    case "ArrowDown" || "Down":
                        console.log("switch", event.key, "down");
                        break;
                }
            });
        </script>

###### 运行结果及报错内容 
控制台：

```javascript
测试.html:13 if ArrowUp up
测试.html:23 switch ArrowUp up
测试.html:13 if ArrowDown up
测试.html:26 switch ArrowDown down
测试.html:13 if ArrowLeft up
测试.html:13 if ArrowRight up

为什么所有的按键都能过 event.key === "ArrowUp" || "Up" 判断

Answer 1

if中的逻辑判断出错了
event.key === "ArrowUp" || "Up"  的执行时候  
第一:先进行event.key === "ArrowUp" 赋值
第二在进行   前面赋值结果 || "Up"  
加入按下 a  
第一 a=== "ArrowUp"    ---->返回false
第二 false|| "Up"     ----->"up"
第三:"up" 在if中进行boolen转化 为true  所以只要按下key if条件始终都是true  
需要调整为
event.key === "ArrowUp"  || event.key === "Up"
if(event.key === "ArrowUp"  || event.key === "Up"){......}