JavaScript:如果只适用于第一个语句？-6ren

JavaScript:如果只适用于第一个语句？

转载作者：行者123 更新时间：2023-11-28 00:18:15

好吧，问题是只有 SHIFT 键起作用？？？它是列表中的第一个 IF，因此由于某种原因它不会出现在其他 IF 中？？？请帮忙:)

更新:有人建议是“else if”导致了问题。我已经尝试过另一种方式。我已经尝试过我能想到的各种方式。请仅发布一个工作示例。谢谢。

另外...如果有人能告诉我为什么关键代码没有显示那就太棒了:)

KeypressCapture.js

//START Screen_Keypress_Capture
function Screen_Keypress_Capture () {
    document.onkeydown = KeyDown_Handler;
    document.onkeyup = KeyUp_Handler;
    var CTRL_Key = false;         
    var SHIFT_Key = false;        
    var ALT_Key = false;
    var JavaScript_Key_Code = -1;

function KeyDown_Handler(ThisEvent) { // (e) is short for event: You can use any name you like (ThisEvent)
                                        // It's a way of passing the same event from one function to another
                                        // START Key-Down Handler
    var Key_Pressed = '';
    if (document.all)
    {
        var Window_Event = window.event;
        Key_Pressed =  Window_Event.keyCode;
    }
    else
    {
        Key_Pressed = ThisEvent.keyCode;
    }
    Detect_Keys_Pressed(Key_Pressed, true);
    Show_Keys_Pressed();
}// END Key-Down Handler

function KeyUp_Handler(ThisEvent) { // START Key-Up Handler
    var Key_Pressed = '';
    if (document.all)
    {
        var Window_Event = window.event;
        Key_Pressed = Window_Event.keyCode;
    }
    else
    {
        Key_Pressed = ThisEvent.keyCode;
    }
    Detect_Keys_Pressed(Key_Pressed, false);
    Show_Keys_Pressed();
}// END Key-Up Handler

function Detect_Keys_Pressed(Key_Pressed, Is_Key_Still_Down) { // START Detect Which Key Is Pressed
    if (Key_Pressed == '16')
    {
        SHIFT_Key = Is_Key_Still_Down;
    }
    else if (Key_Pressed == '17')
    {
        CTRL_Key = Is_Key_Still_Down;
    }
    else if (Key_Pressed == '18')
    {
        ALT_Key = Is_Key_Still_Down;
    }
    else
    {
        if(Is_Key_Still_Down)
            JavaScript_Key_Code = Key_Pressed;
        else
            JavaScript_Key_Code = -1;
    }   
}// END Detect Which Key Is Pressed

function Show_Keys_Pressed() { // START Show Results IN DIV's
// Example to move a div
// var dest = document.getElementById("my_div");
// var orig = document.getElementById("ad_div");
// orig.parentNode.removeChild(orig);
// dest.appendChild(orig);
    var Show_Current_Keys_Pressed = document.getElementById('Show_Current_Keys_Pressed');
    var DIV_Shift = document.getElementById('DIV_Shift');
    var DIV_Ctrl = document.getElementById('DIV_Ctrl');
    var DIV_Alt = document.getElementById('DIV_Alt');
    var DIV_Char = document.getElementById('DIV_Char');

    if(SHIFT_Key == true){
        DIV_Shift.parentNode.removeChild(DIV_Shift);
        Show_Current_Keys_Pressed.appendChild(DIV_Shift);
        DIV_Shift.style.visibility = "visible";
    }

    else if(SHIFT_Key == false){
        DIV_Shift.style.visibility = "hidden";
        Show_Current_Keys_Pressed.parentNode.removeChild(DIV_Shift);
        body.appendChild(DIV_Shift);    
    }

    else if(CTRL_Key == true){
        DIV_Ctrl.parentNode.removeChild(DIV_Ctrl);
        Show_Current_Keys_Pressed.appendChild(DIV_Ctrl);
        DIV_Ctrl.style.visibility = "visible";
    }

    else if(CTRL_Key == false){
        DIV_Ctrl.style.visibility = "hidden";
        Show_Current_Keys_Pressed.parentNode.removeChild(DIV_Ctrl);
        body.appendChild(DIVCtrl);
    }

    else if(ALT_Key == true){
        DIV_Alt.parentNode.removeChild(DIV_Alt);
        Show_Current_Keys_Pressed.appendChild(DIV_Alt);
        DIV_Alt.style.visibility = "visible";
    }

    else if(CTRL_Key == false){
        DIV_Alt.style.visibility = "hidden";
        Show_Current_Keys_Pressed.parentNode.removeChild(DIV_Alt);
        body.appendChild(DIV_Alt);
    }

    else if(JavaScript_Key_Code == true){
        DIV_Char.parentNode.removeChild(DIV_Char);
        Show_Current_Keys_Pressed.appendChild(DIV_Char);
        DIV_Char.innerHTML = JavaScript_Key_Code;   
        DIV_Char.style.visibility = "visible";
    }

    else if(JavaScript_Key_Code == false){
        DIV_Char.style.visibility = "hidden";
        DIV_Char.innerHTML = JavaScript_Key_Code;   
        Show_Current_Keys_Pressed.parentNode.removeChild(DIV_Char);
        body.appendChild(DIV_Char);
    }

    else{}

}// END Show Results IN DIV's

}
// END Screen_Keypress_Capture

KeypressCapture.css

包含 CSS:href="KeypressCapture.css"rel="stylesheet"type="text/css"

包含 JavaScript:src="KeypressCapture.js"

    #Show_Current_Keys_Pressed {
    width: 400px;
    height: 21px;
    padding: 20px 20px 20px 30px; /* UP RIGHT DOWN LEFT */
    margin: 40px;
    border: 1px solid #999;
    border-radius:4px;
    -moz-border-radius:4px;
    -webkit--moz-border-radius:4px;
    background-color: #fff;
    clear: both;
    float: left;
}

#Show_Current_Combo {
    width: 400px;
    height: 21px;
    padding: 20px 20px 20px 30px; /* UP RIGHT DOWN LEFT */
    margin: 40px;
    margin-top: 0px;
    border: 1px solid #999;
    border-radius:4px;
    -moz-border-radius:4px;
    -webkit--moz-border-radius:4px;
    background-color: #FCFFA8;
    clear: both;
    float: left;
}

#Show_Created_String {
    width: 400px;
    height: 21px;
    padding: 20px 20px 20px 30px; /* UP RIGHT DOWN LEFT */
    margin: 40px;
    margin-top: 0px;
    border: 1px solid #999;
    border-radius:4px;
    -moz-border-radius:4px;
    -webkit--moz-border-radius:4px;
    background-color: #FFE2C6;
    clear: both;
    float: left;
}

#DIV_Shift {
    font: Arial, Gotham, "Helvetica Neue", Helvetica, sans-serif;
    font-size: 24px;
    font-weight: bold;
    color: red;
    visibility: hidden;
    float: left;
}

#DIV_Ctrl {
    font: Arial, Gotham, "Helvetica Neue", Helvetica, sans-serif;
    font-size: 24px;
    font-weight: bold;
    color: green; 
    visibility: hidden;
    float: left;
}

#DIV_Alt {
    font: Arial, Gotham, "Helvetica Neue", Helvetica, sans-serif;
    font-size: 24px;
    font-weight: bold;
    color: blue; 
    visibility: hidden;
    float: left;
}

#DIV_Char {
    font: Arial, Gotham, "Helvetica Neue", Helvetica, sans-serif;
    font-size: 24px;
    font-weight: bold;
    color: black; 
    visibility: hidden;
    float: left;

}

.STYLE_Shift {
    font: Arial, Gotham, "Helvetica Neue", Helvetica, sans-serif;
    font-size: 24px;
    font-weight: bold;
    color: red; 
    visibility: hidden;
    float: left;
}

.STYLE_Ctrl {
    font: Arial, Gotham, "Helvetica Neue", Helvetica, sans-serif;
    font-size: 24px;
    font-weight: bold;
    color: green; 
    visibility: hidden;
    float: left;
}

.STYLE_Alt {
    font: Arial, Gotham, "Helvetica Neue", Helvetica, sans-serif;
    font-size: 24px;
    font-weight: bold;
    color: blue; 
    visibility: hidden;
    float: left;
}

.STYLE_Char {
    font: Arial, Gotham, "Helvetica Neue", Helvetica, sans-serif;
    font-size: 24px;
    font-weight: bold;
    color: black; 
    visibility: hidden;
    float: left;
}

KeypressCapture..html

<div id="Show_Current_Keys_Pressed">
</div>

<div id="Show_Current_Combo">
</div>

<div id="Show_Created_String">
</div>


<div id="DIV_Shift">
SHIFT
</div>

<div id="DIV_Ctrl">
CTRL
</div>

<div id="DIV_Alt">
ALT
</div>

<div id="DIV_Char">
</div>

更新:即使您使用以下代码，它仍然只运行列表中的第一个，即“SHIFT”键，并跳过其他键。

        if(SHIFT_Key){
            DIV_Shift.parentNode.removeChild(DIV_Shift);
            Show_Current_Keys_Pressed.appendChild(DIV_Shift);
            DIV_Shift.style.visibility = "visible";
        }else{          
            DIV_Shift.style.visibility = "hidden";
            Show_Current_Keys_Pressed.parentNode.removeChild(DIV_Shift);
            body.appendChild(DIV_Shift);            
        }

        if(CTRL_Key){
            DIV_Ctrl.parentNode.removeChild(DIV_Ctrl);
            Show_Current_Keys_Pressed.appendChild(DIV_Ctrl);
            DIV_Ctrl.style.visibility = "visible";
        }else{ 
            DIV_Ctrl.style.visibility = "hidden";
            Show_Current_Keys_Pressed.parentNode.removeChild(DIV_Ctrl);
            body.appendChild(DIVCtrl);
        }

        if(ALT_Key){
            DIV_Alt.parentNode.removeChild(DIV_Alt);
            Show_Current_Keys_Pressed.appendChild(DIV_Alt);
            DIV_Alt.style.visibility = "visible";
        }else{ 
            DIV_Alt.style.visibility = "hidden";
            Show_Current_Keys_Pressed.parentNode.removeChild(DIV_Alt);
            body.appendChild(DIV_Alt);
        }

        if(JavaScript_Key_Code){
            DIV_Char.parentNode.removeChild(DIV_Char);
            Show_Current_Keys_Pressed.appendChild(DIV_Char);
            DIV_Char.innerHTML = JavaScript_Key_Code;   
            DIV_Char.style.visibility = "visible";
        }else{ 
            DIV_Char.style.visibility = "hidden";
            DIV_Char.innerHTML = JavaScript_Key_Code;   
            Show_Current_Keys_Pressed.parentNode.removeChild(DIV_Char);
            body.appendChild(DIV_Char);
        }

最佳答案

问题在于您使用了else if。仅当前面的所有 block 都为 false 时，它才执行该 block 。但你的代码看起来像这样:

if(SHIFT_Key == true){
    ...
}
else if(SHIFT_Key == false){
    ...  
}
else if(CTRL_Key == true){
    ...
}

如果第一个 if 失败，则保证第二个成功(SHIFT_Key 为 true 或 false)。因此下一个 else 将永远不会被使用。

您应该单独测试每个键，而不使用 else if。

下一个问题:JavaScript_Key_Code 不是 true/false；当没有按下任何键时，它设置为-1，或者当按键按下时设置为键代码。所以你应该将它与-1进行比较。

下一个问题:您的 else 子句中有 body.appendChild(DIV_Shift);，但没有变量 body，它是 文档.body.

下一个问题:您有一个拼写错误，DIVCtrl 应该是 DIV_Ctrl。

下一个问题:每个 else block 都会执行类似 Show_Current_Keys_Pressed.parentNode.removeChild(DIV_Shift); 的操作。但是在您第一次按下不同的键后，该 DIV 不再是该父节点的子节点，而是被重新定位到主体。此错误导致该功能停止。在移动它之前，您需要测试它当前是否位于该节点中。

//START Screen_Keypress_Capture
function Screen_Keypress_Capture() {
    document.onkeydown = KeyDown_Handler;
    document.onkeyup = KeyUp_Handler;
    var CTRL_Key = false;
    var SHIFT_Key = false;
    var ALT_Key = false;
    var JavaScript_Key_Code = -1;

    function KeyDown_Handler(ThisEvent) { // (e) is short for event: You can use any name you like (ThisEvent)
        // It's a way of passing the same event from one function to another
        // START Key-Down Handler
        var Key_Pressed = '';
        if (document.all) {
            var Window_Event = window.event;
            Key_Pressed = Window_Event.keyCode;
        } else {
            Key_Pressed = ThisEvent.keyCode;
        }
        Detect_Keys_Pressed(Key_Pressed, true);
        Show_Keys_Pressed();
    } // END Key-Down Handler

    function KeyUp_Handler(ThisEvent) { // START Key-Up Handler
        var Key_Pressed = '';
        if (document.all) {
            var Window_Event = window.event;
            Key_Pressed = Window_Event.keyCode;
        } else {
            Key_Pressed = ThisEvent.keyCode;
        }
        Detect_Keys_Pressed(Key_Pressed, false);
        Show_Keys_Pressed();
    } // END Key-Up Handler

    function Detect_Keys_Pressed(Key_Pressed, Is_Key_Still_Down) { // START Detect Which Key Is Pressed
        if (Key_Pressed == '16') {
            SHIFT_Key = Is_Key_Still_Down;
        } else if (Key_Pressed == '17') {
            CTRL_Key = Is_Key_Still_Down;
        } else if (Key_Pressed == '18') {
            ALT_Key = Is_Key_Still_Down;
        } else {
            if (Is_Key_Still_Down) JavaScript_Key_Code = Key_Pressed;
            else JavaScript_Key_Code = -1;
        }
    } // END Detect Which Key Is Pressed

    function Show_Keys_Pressed() { // START Show Results IN DIV's
        // Example to move a div
        // var dest = document.getElementById("my_div");
        // var orig = document.getElementById("ad_div");
        // orig.parentNode.removeChild(orig);
        // dest.appendChild(orig);
        var Show_Current_Keys_Pressed = document.getElementById('Show_Current_Keys_Pressed');
        var DIV_Shift = document.getElementById('DIV_Shift');
        var DIV_Ctrl = document.getElementById('DIV_Ctrl');
        var DIV_Alt = document.getElementById('DIV_Alt');
        var DIV_Char = document.getElementById('DIV_Char');
        var body = document.body;

        if (SHIFT_Key == true) {
            DIV_Shift.parentNode.removeChild(DIV_Shift);
            Show_Current_Keys_Pressed.appendChild(DIV_Shift);
            DIV_Shift.style.visibility = "visible";
        } else {
            if (DIV_Shift.parentNode != body) {
                DIV_Shift.style.visibility = "hidden";
                Show_Current_Keys_Pressed.parentNode.removeChild(DIV_Shift);
                body.appendChild(DIV_Shift);
            }
        }

        if (CTRL_Key == true) {
            DIV_Ctrl.parentNode.removeChild(DIV_Ctrl);
            Show_Current_Keys_Pressed.appendChild(DIV_Ctrl);
            DIV_Ctrl.style.visibility = "visible";
        } else {
            if (DIV_Ctrl.parentNode != body) {
                DIV_Ctrl.style.visibility = "hidden";
                Show_Current_Keys_Pressed.parentNode.removeChild(DIV_Ctrl);
                body.appendChild(DIV_Ctrl);
            }
        }

        if (ALT_Key == true) {
            DIV_Alt.parentNode.removeChild(DIV_Alt);
            Show_Current_Keys_Pressed.appendChild(DIV_Alt);
            DIV_Alt.style.visibility = "visible";
        } else {
            if (DIV_Alt.parentNode != body) {
                DIV_Alt.style.visibility = "hidden";
                Show_Current_Keys_Pressed.parentNode.removeChild(DIV_Alt);
                body.appendChild(DIV_Alt);
            }
        }

        if (JavaScript_Key_Code != -1) {
            DIV_Char.parentNode.removeChild(DIV_Char);
            Show_Current_Keys_Pressed.appendChild(DIV_Char);
            DIV_Char.innerHTML = JavaScript_Key_Code;
            DIV_Char.style.visibility = "visible";
        } else {
            if (DIV_Char.parentNode != body) {
                DIV_Char.style.visibility = "hidden";
                DIV_Char.innerHTML = JavaScript_Key_Code;
                Show_Current_Keys_Pressed.parentNode.removeChild(DIV_Char);
            }
            body.appendChild(DIV_Char);
        }

    } // END Show Results IN DIV's

}
// END Screen_Keypress_Capture
Screen_Keypress_Capture();

#Show_Current_Keys_Pressed {
    width: 400px;
    height: 21px;
    padding: 20px 20px 20px 30px;
    /* UP RIGHT DOWN LEFT */
    margin: 40px;
    border: 1px solid #999;
    border-radius:4px;
    -moz-border-radius:4px;
    -webkit--moz-border-radius:4px;
    background-color: #fff;
    clear: both;
    float: left;
}
#Show_Current_Combo {
    width: 400px;
    height: 21px;
    padding: 20px 20px 20px 30px;
    /* UP RIGHT DOWN LEFT */
    margin: 40px;
    margin-top: 0px;
    border: 1px solid #999;
    border-radius:4px;
    -moz-border-radius:4px;
    -webkit--moz-border-radius:4px;
    background-color: #FCFFA8;
    clear: both;
    float: left;
}
#Show_Created_String {
    width: 400px;
    height: 21px;
    padding: 20px 20px 20px 30px;
    /* UP RIGHT DOWN LEFT */
    margin: 40px;
    margin-top: 0px;
    border: 1px solid #999;
    border-radius:4px;
    -moz-border-radius:4px;
    -webkit--moz-border-radius:4px;
    background-color: #FFE2C6;
    clear: both;
    float: left;
}
#DIV_Shift {
    font: Arial, Gotham, "Helvetica Neue", Helvetica, sans-serif;
    font-size: 24px;
    font-weight: bold;
    color: red;
    visibility: hidden;
    float: left;
}
#DIV_Ctrl {
    font: Arial, Gotham, "Helvetica Neue", Helvetica, sans-serif;
    font-size: 24px;
    font-weight: bold;
    color: green;
    visibility: hidden;
    float: left;
}
#DIV_Alt {
    font: Arial, Gotham, "Helvetica Neue", Helvetica, sans-serif;
    font-size: 24px;
    font-weight: bold;
    color: blue;
    visibility: hidden;
    float: left;
}
#DIV_Char {
    font: Arial, Gotham, "Helvetica Neue", Helvetica, sans-serif;
    font-size: 24px;
    font-weight: bold;
    color: black;
    visibility: hidden;
    float: left;
}
.STYLE_Shift {
    font: Arial, Gotham, "Helvetica Neue", Helvetica, sans-serif;
    font-size: 24px;
    font-weight: bold;
    color: red;
    visibility: hidden;
    float: left;
}
.STYLE_Ctrl {
    font: Arial, Gotham, "Helvetica Neue", Helvetica, sans-serif;
    font-size: 24px;
    font-weight: bold;
    color: green;
    visibility: hidden;
    float: left;
}
.STYLE_Alt {
    font: Arial, Gotham, "Helvetica Neue", Helvetica, sans-serif;
    font-size: 24px;
    font-weight: bold;
    color: blue;
    visibility: hidden;
    float: left;
}
.STYLE_Char {
    font: Arial, Gotham, "Helvetica Neue", Helvetica, sans-serif;
    font-size: 24px;
    font-weight: bold;
    color: black;
    visibility: hidden;
    float: left;
}

<div id="Show_Current_Keys_Pressed"></div>
<div id="Show_Current_Combo"></div>
<div id="Show_Created_String"></div>
<div id="DIV_Shift">SHIFT</div>
<div id="DIV_Ctrl">CTRL</div>
<div id="DIV_Alt">ALT</div>
<div id="DIV_Char"></div>

关于JavaScript:如果只适用于第一个语句？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/30268732/

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JavaScript:如果只适用于第一个语句？