按下向上和向下键时触发功能？

Question

我想要它，所以当按下向上或向下键时它会触发不同的功能。到目前为止，这是我的代码：

window.addEventListener('keypress', function(e) {

    console.log("A Key has been pressed");

    /*Sets "key" variable to be the value of the key code of the key pressed*/
    var key = e.which || e.keyCode;

    /*checks if key pressed is the "up" key*/
    if (key === 38){
            functionOne();
            console.log("Up key was Pressed");
        }

    /*checks if key pressed is the "down" key*/     
    else if (key === 40){
            functionTwo();
            console.log("Down key was Pressed");
        }
    })

每当我按下除箭头键、shift、alt、caps、tab 和 f1 - f12 之外的任何键时，显示 "A key has been pressed" 的控制台日志都会激活。可能是什么原因造成的？

先谢谢你。

Answer 1

改为使用 keyup 事件。

The onkeypress event is not fired for all keys (e.g. ALT, CTRL, SHIFT, ESC, arrows) in all browsers. To detect only whether the user has pressed a key, use the onkeydown event instead, because it works for all keys.

window.addEventListener('keyup', function(e) {
var key = e.which || e.keyCode;
    console.log(key);
    if (key === 38){
        console.log("Up key was Pressed", key );
    }    
    else if (key === 40){
        console.log("Down key was Pressed", key );
    }
    e.preventDefault();
})

按下向上和向下键时触发功能？

To have a function triggered when up and down key is pressed?

javascript

if-statement

function

keycode

addeventlistener