Detailed introduction to the usage of single-select and multiple-select tags in HTML

The

select element creates a single-select or multiple-select menu. When submitting a form, the browser will submit the selected items, or collect multiple options separated by commas. The following is an example of its specific usage. The select element creates single-select or multiple-select menus. When the form is submitted, the browser submits the selected items, or collects multiple comma-separated options, combines them into a single parameter list, and includes the name attribute when submitting the 221f08282418e2996498697df914ce4e form data to the server.

1. Basic usage:

The code is as follows:

<select> 
<option value ="volvo">Volvo</option> 
<option value ="saab">Saab</option> 
<option value="opel">Opel</option> 
<option value="audi">Audi</option> 
</select>

Among them, the 4afa15d3069109ac30911f04c56f3338 tag can be omitted and used in the page

The code is as follows:

<SELECT NAME="studyCenter" id="studyCenter" SIZE="1"> 
<OPTION VALUE="0">全部 
<OPTION VALUE="1">湖北电大网络学习中心 
<OPTION VALUE="2">成都师范学院网络学习中心 
<OPTION VALUE="3">武汉职业技术学院网络学习中心 
</SELECT>

2. The Select element can also be used for multiple selections, see the following code:

The code is as follows:

//有multiple属性，则可以多选 
<select name= “education” id=”education” multiple=”multiple”> 
<option value=”1”>高中</option> 
<option value=”2”>大学</option> 
<option value=”3”>博士</option> 
</select> 
//下面没有multiple属性 , 只显示一条，不能多选 
<select name= “education” id=”education” > 
<option value=”1”>高中</option> 
<option value=”2”>大学</option> 
<option value=”3”>博士</option> 
</select> 
//下面是设置了size属性的情况 , 如果size = 3 那么就显示三条数据，注意不能多选的。 
<select name="education" id="education" size=&#39;3&#39;> 
<option value="0">小学</option> 
<option value="1">初中</option> 
<option value="2">高中</option> 
<option value="3">中专</option> 
<option value="4">大专</option> 
<option value="5">本科</option> 
<option value="6">研究生</option> 
<option value="7">博士</option> 
<option value="8">博士后</option> 
<option selected>请选择</option> 
</select>

3. All common operations involved in the multi-select Select component:

1. Determine whether there is an Item with a specified value in the select option

The code is as follows:

@param objSelectId 将要验证的目标select组件的id 
@param objItemValue 将要验证是否存在的值 
function isSelectItemExit(objSelectId,objItemValue) { 
var objSelect = document.getElementById(objSelectId); 
var isExit = false; 
if (null != objSelect && typeof(objSelect) != "undefined") { 
for(var i=0;i<objSelect.options.length;i++) { 
if(objSelect.options[i].value == objItemValue) { 
isExit = true; 
break; 
} 
} 
} 
return isExit; 
}

2. Add an Item to the select option

The code is as follows:

@param objSelectId 将要加入item的目标select组件的id 
@param objItemText 将要加入的item显示的内容 
@param objItemValue 将要加入的item的值 
function addOneItemToSelect(objSelectId,objItemText,objItemValue) { 
var objSelect = document.getElementById(objSelectId); 
if (null != objSelect && typeof(objSelect) != "undefined") { 
//判断是否该值的item已经在select中存在 
if(isSelectItemExit(objSelectId,objItemValue)) { 
$.messager.alert('提示消息','该值的选项已经存在!','info'); 
} else { 
var varItem = new Option(objItemText,objItemValue); 
objSelect.options.add(varItem); 
} 
} 
}

3. Delete the selected item from the select option, support multiple selections and multiple deletions

The code is as follows:

@param objSelectId 将要进行删除的目标select组件id 
function removeSelectItemsFromSelect(objSelectId) { 
var objSelect = document.getElementById(objSelectId); 
var delNum = 0; 
if (null != objSelect && typeof(objSelect) != "undefined") { 
for(var i=0;i<objSelect.options.length;i=i+1) { 
if(objSelect.options[i].selected) { 
objSelect.options.remove(i); 
delNum = delNum + 1; 
i = i - 1; 
} 
} 
if (delNum <= 0 ) { 
$.messager.alert(&#39;提示消息&#39;,&#39;请选择你要删除的选项!&#39;,&#39;info&#39;); 
} else { 
$.messager.alert(&#39;提示消息&#39;,&#39;成功删除了&#39;+delNum+&#39;个选项!&#39;,&#39;info&#39;); 
} 
} 
}

4. Delete an Item from the select option according to the specified value

The code is as follows:

@param objSelectId 将要验证的目标select组件的id 
@param objItemValue 将要验证是否存在的值 
function removeItemFromSelectByItemValue(objSelectId,objItemValue) { 
var objSelect = document.getElementById(objSelectId); 
if (null != objSelect && typeof(objSelect) != "undefined") { 
//判断是否存在 
if(isSelectItemExit(objSelect,objItemValue)) { 
for(var i=0;i<objSelect.options.length;i++) { 
if(objSelect.options[i].value == objItemValue) { 
objSelect.options.remove(i); 
break; 
} 
} 
$.messager.alert(&#39;提示消息&#39;,&#39;成功删除!&#39;,&#39;info&#39;); 
} else { 
$.messager.alert(&#39;提示消息&#39;,&#39;不存在指定值的选项!&#39;,&#39;info&#39;); 
} 
} 
}

5. Clear all options in the select

The code is as follows:

@param objSelectId 将要进行清空的目标select组件id 
function clearSelect(objSelectId) { 
var objSelect = document.getElementById(objSelectId); 
if (null != objSelect && typeof(objSelect) != "undefined") { 
for(var i=0;i<objSelect.options.length;) { 
objSelect.options.remove(i); 
} 
} 
}

6. Get all the items in the select and assemble all values ​​into one character String, separated by commas between values ​​

The code is as follows:

@param objSelectId 目标select组件id 
@return select中所有item的值，值与值之间用逗号隔开 
function getAllItemValuesByString(objSelectId) { 
var selectItemsValuesStr = ""; 
var objSelect = document.getElementById(objSelectId); 
if (null != objSelect && typeof(objSelect) != "undefined") { 
var length = objSelect.options.length 
for(var i = 0; i < length; i = i + 1) { 
if (0 == i) { 
selectItemsValuesStr = objSelect.options[i].value; 
} else { 
selectItemsValuesStr = selectItemsValuesStr + "," + objSelect.options[i].value; 
} 
} 
} 
return selectItemsValuesStr; 
}

7. Move all selected options in one select to another select Go

The code is as follows:

@param fromObjSelectId 移动item的原select组件id 
@param toObjectSelectId 移动item将要进入的目标select组件id 
function moveAllSelectedToAnotherSelectObject(fromObjSelectId, toObjectSelectId) { 
var objSelect = document.getElementById(fromObjSelectId); 
var delNum = 0; 
if (null != objSelect && typeof(objSelect) != "undefined") { 
for(var i=0;i<objSelect.options.length;i=i+1) { 
if(objSelect.options[i].selected) { 
addOneItemToSelect(toObjectSelectId,objSelect.options[i].text,objSelect.options[i].value) 
objSelect.options.remove(i); 
i = i - 1; 
} 
} 
} 
}

8. Move all options in one select to another select

The code is as follows :

@param fromObjSelectId 移动item的原select组件id 
@param toObjectSelectId 移动item将要进入的目标select组件id 
function moveAllToAnotherSelectObject(fromObjSelectId, toObjectSelectId) { 
var objSelect = document.getElementById(fromObjSelectId); 
if (null != objSelect) { 
for(var i=0;i<objSelect.options.length;i=i+1) { 
addOneItemToSelect(toObjectSelectId,objSelect.options[i].text,objSelect.options[i].value) 
objSelect.options.remove(i); 
i = i - 1; 
} 
} 
}

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