我正在尝试解决这个问题，但我需要一些帮助。一个带有添加到购物车按钮的下拉菜单，如果不选择任何选项就不会提交，我想要的是一个弹出窗口，提示从每个下拉选项中选择一个(必需)。这就是我想要做的http://ccaples.com/index.php/basic-scripts/examples-i/dropdown-menus-that-require-selection ，问题是如何在我的代码中实现这一点，非常感谢。
<SCRIPT TYPE="text/javascript">
function MM_goToURL() { //v3.0
var i, args=MM_goToURL.arguments; document.MM_returnValue = false;
for (i=0; i<(args.length-1); i+=2) eval(args[i]+".location='"+args[i+1]+"'");
}
function Dollar (val) { // force to valid dollar amount
var str,pos,rnd=0;
if (val < .995) rnd = 1; // for old Netscape browsers
str = escape (val*1.0 + 0.005001 + rnd); // float, round, escape
pos = str.indexOf (".");
if (pos > 0) str = str.substring (rnd, pos + 3);
return str;
}
function ReadForm (obj1) { // process un-named selects
var i,j,amt,des,obj,pos,tok,val;
var ary = new Array ();
amt = obj1.baseamt.value*1.0; // base amount
des = obj1.basedes.value; // base description
for (i=0; i<obj1.length; i++) { // run entire form
obj = obj1.elements[i]; // a form element
if (obj.type == "select-one" && // just get selects
obj.name == "") { // must be un-named
pos = obj.selectedIndex; // which option selected
val = obj.options[pos].value; // selected value
ary = val.split (" "); // break apart
for (j=0; j<ary.length; j++) { // look at all items
// first we do single character tokens...
if (ary[j].length < 2) continue;
tok = ary[j].substring (0,1); // first character
val = ary[j].substring (1); // get data
if (tok == "@") amt = val * 1.0;
if (tok == "+") amt = amt + val*1.0;
if (tok == "%") amt = amt + (amt * val/100.0);
if (tok == "#") { // record item number
if (obj1.item_number) obj1.item_number.value = val;
ary[j] = ""; // zap this array element
}
// Now we do 3-character tokens...
if (ary[j].length < 4) continue;
tok = ary[j].substring (0,3); // first 3 chars
val = ary[j].substring (3); // get data
if (tok == "s1=") { // value for shipping
if (obj1.shipping) obj1.shipping.value = val;
ary[j] = ""; // clear it out
}
if (tok == "s2=") { // value for shipping2
if (obj1.shipping2) obj1.shipping2.value = val;
ary[j] = ""; // clear it out
}
}
val = ary.join (" "); // rebuild val with what's left
if (des.length == 0) des = val; // 1st storage?
else des = des + ", " + val; // nope, accumulate value
}
}
obj1.item_name.value = des;
obj1.amount.value = Dollar (amt);
if (obj1.tot) obj1.tot.value = "$" + Dollar (amt);
}
</SCRIPT><FORM id=viewcart name=viewcart action=https://www.paypal.com/cgi-bin/webscr
method=post>
</FORM>
<FORM onSubmit="this.target = 'paypal'; ReadForm (this.form);"
action=https://www.paypal.com/cgi-bin/webscr method=post>
<P>
<INPUT type=hidden value=_cart name=cmd>
<INPUT type=hidden value=1 name=add>
<INPUT type=hidden value=my@email.com name=business>
<INPUT type=hidden name=item_name>
<INPUT type=hidden name=item_number>
<INPUT type=hidden name=amount>
<INPUT type=hidden value=USD name=currency_code>
<INPUT type=hidden value=USD name=lc>
<INPUT type=hidden value=00 name=shipping>
<INPUT type=hidden value=00.00 name=baseamt>
<INPUT type=hidden VALUE="itemname" name=basedes>
<INPUT TYPE="hidden" NAME="on0" VALUE="Details">
<INPUT TYPE="hidden" NAME="os0" VALUE="moredetails" MAXLENGTH="800">
<BR>
<BR>
</P>
<TABLE WIDTH="400px" BORDER="0" CELLPADDING="0" CELLSPACING="0" align="right">
<TR>
<TD ALIGN="left">
<p class="heading"> </p>
<p class="main"> dropdown1</p>
<p class="heading"> </p>
</TD>
<TD>
<SELECT STYLE="WIDTH: 240px" onChange="ReadForm (this.form);">
<OPTION selected>Please select </OPTION>
<OPTION VALUE="option1 +125.00">option1</OPTION>
<OPTION VALUE="option2 +90.00">option2</OPTION>
<OPTION VALUE="option3 +40.00">option3</OPTION>
</SELECT>
</TD>
</TR>
<TR>
<TD ALIGN="left">
<p class="heading"> </p>
<p class="main"> dropdown2</p>
<p class="heading"> </p>
</TD>
<TD>
<SELECT STYLE="WIDTH: 240px" onChange="ReadForm (this.form);">
<OPTION selected>Please select </OPTION>
<OPTION VALUE="option1 +55.00">option1</OPTION>
<OPTION VALUE="option2 +99.00">option2</OPTION>
<OPTION VALUE="option3 +44.00">option3</OPTION>
</SELECT>
</TD>
</TR>
<tr>
<TR>
<TD ALIGN="left">
<p class="main"> </p>
<p class="main"> Price</p>
<p class="main"> </p>
</TD>
<TD ALIGN="left">
<INPUT class=nbor size=8 value=00.00 name=tot>
</TD>
</TR>
<TD align="left">
<label for="submit"></label>
<TD align="left">
<input type="image" src="/addtocart2.png" name="submit" id="submit" value="submit" >
</div>
</div></td>
</tr>
</table>
</table>
</form>
</TABLE>
</FORM>
</div> 最佳答案
您只需添加一个表单验证函数并为元素提供一些 ID，以便您的验证函数知道要验证什么。
首先，在你的<script>下添加这个函数标签。
function validate_first() {
var msg1 = "Please select from first dropdown\n";
var msg2 = "Please select from second dropdown";
var first = document.getElementById('select1').value;
var second = document.getElementById('select2').value;
if(first=="" || second=="") {
alert(((first == "") ? msg1 : "") + ((second == "") ? msg2 : ""));
return false;
}
return true;
}
然后更改onsubmit表单定义中的值如下:
<FORM onSubmit="this.target = 'paypal'; return validate_first();" action=https://www.paypal.com/cgi-bin/webscr method=post>
最后，为下拉菜单提供一些 ID，并为“请选择”选项添加实际值。
对于第一个下拉列表:
<SELECT id="select1" STYLE="WIDTH: 240px" onChange="ReadForm (this.form);">
<OPTION value="" selected>Please select </OPTION>
<OPTION VALUE="option1 +125.00">option1</OPTION>
<OPTION VALUE="option2 +90.00">option2</OPTION>
<OPTION VALUE="option3 +40.00">option3</OPTION>
</SELECT>
第二个:
<SELECT id="select2" STYLE="WIDTH: 240px" onChange="ReadForm (this.form);">
<OPTION value="" selected>Please select </OPTION>
<OPTION VALUE="option1 +55.00">option1</OPTION>
<OPTION VALUE="option2 +99.00">option2</OPTION>
<OPTION VALUE="option3 +44.00">option3</OPTION>
</SELECT>
就是这样。
关于javascript - 需要选择的下拉菜单，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/31626130/