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[英]how do I add an option to a html form dropdown list with javascript
[英]How do I disable form dropdown option using javascript
我試圖在頁面加載后在下拉列表中選擇“選擇”時禁用表單中的“名稱”文本字段(在頁面加載時被禁用),即在我選擇了其他兩個選項之一之后禁用或啟用該字段,當我返回“選擇”時,我希望禁用同一字段。 我不明白為什么我編寫的JavaScript可以防止這種情況的發生。 謝謝!
<script type="text/javascript">
function clickclear(thisfield, defaulttext) {
if (thisfield.value === defaulttext) {
thisfield.value = "";
}
}
function clickrecall(thisfield, defaulttext) {
if (thisfield.value === "") {
thisfield.value = defaulttext;
}
}
function checkPickup() {
if (form.os0.value != "Pickup from Toowong, Brisbane" ) {
form.name.disabled = false; form.name.style.color = '#333';
} else {
form.name.disabled = true; form.name.style.color = '#CCC';
/* Reset form values */
form.name.value = "His/her name";
}
}
</script>
<script type="text/javascript">
function validate(form) {
var errmsg = "Oops, you're required to complete the following fields! \n";
// Various other form validations here
// Validate "Pickup"
if (form.os0.value === "") {
errmsg = errmsg + " - Choose pickup or delivery\n";
}
// Validate "phone"
if (form.phone.value === "" || form.phone.value === "Mobile's best!") {
errmsg = errmsg + " - Your phone number\n";
}
if (form.os0.value != "Pickup from Toowong, Brisbane") {
// Validate "name"
if (form.name.value === "" || form.name.value === "His/her name") {
errmsg = errmsg + " - His/her name\n";
}
}
// Alert if fields are empty and cancel form submit
if (errmsg === "Oops, you're required to complete the following fields! \n") {
form.submit();
} else {
alert(errmsg);
return false;
}
}
</script>
</head>
<body>
<form name="form" action="https://www.paypal.com/cgi-bin/webscr" method="post" onSubmit="return validate(form)">
<p class="row">
<input type="hidden" name="on0" value="Pickup and delivery" />Pickup and delivery<br />
<select name="os0" onchange="checkPickup()">
<option value="" selected >Choose</option>
<option value="Pickup from Toowong, Brisbane">Pickup from Toowong, Brisbane $1.00 AUD</option>
<option value="Brisbane +$23.60">Brisbane +$23.60 =$1.00 AUD</option>
</select>
</p>
<p class="row">Your daytime phone number<br />
<input type="text" name="phone" value="Mobile's best!" onclick="clickclear(this, 'Mobile\'s best!')" onblur="clickrecall(this,'Mobile\'s best!')" />
</p>
<p class="row">Recipient's name<br />
<input style="color: #ccc" class="name" type="text" name="name" value="His/her name" onclick="clickclear(this, 'His/her name')" onblur="clickrecall(this,'His/her name')" disabled />
</p>
<input name="custom" type="hidden" />
<input type="hidden" name="currency_code" value="AUD" />
<input class="button" type="image" src="https://www.paypalobjects.com/en_AU/i/btn/btn_buynowCC_LG.gif" border="0" name="submit" alt="PayPal — The safer, easier way to pay online." />
<img alt="" border="0" src="https://www.paypalobjects.com/en_AU/i/scr/pixel.gif" width="1" height="1"> -->
</form>
</body>
</html>
這可能是對您所寫內容的簡單誤解:
if (form.os0.value != "Pickup from Toowong, Brisbane" ) {
form.name.disabled = false; form.name.style.color = '#333';
} else {
form.name.disabled = true; form.name.style.color = '#CCC';
//
}
普通英語翻譯如下:
如果該值不是
"Pickup from Toowong, Brisbane"
,則啟用該字段,否則禁用它。
等效於:
僅當值為
"Pickup from Toowong, Brisbane"
時禁用該字段。
我相信您要尋找的邏輯是:
if (form.os0.value == "Brisbane +$23.60" ) {
form.name.disabled = false; form.name.style.color = '#333';
} else {
form.name.disabled = true; form.name.style.color = '#CCC';
//
}
由於涉及特定案例,使用switch
語句編寫代碼可能更漂亮。
您打算在問題中輸入等於(==)的double還是等於(===)的三倍? 基於查看您的代碼,在我看來,您需要一個等於(==)的雙精度數而不是三進制。 我認為三重可能意味着其他。
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