Of Stack

Brief introduction to Option objects in drop down menu

  • 2020-06-07 04:02:51
  • OfStack

1. Create the Option object

1.1 var optionEle1 = document.createElement('option');

1.2 var optionEle2 = new Option(text, value, defaultSelected, selected);

2. options properties

2.1 select.options returns the collection of Option objects under the select tag

3. Empty the drop-down menu

3.1 Using for loop delete, note the dynamic change of array length

3.2 select. options. length = 0;

4. The application 


<html> 
<head> 
<script language="javascript"> 
function number(){ 
var obj = document.getElementById("mySelect"); 
//obj.options[obj.selectedIndex] = new Option(" My taste ","4");// Change in the value of the currently selected one  
//obj.options.add(new Option(" My taste ","4")); add 1 a option 
//alert(obj.selectedIndex);// Show the serial number, option Self-Set  
//obj.options[obj.selectedIndex].text = " My taste "; Change the value  
//obj.remove(obj.selectedIndex); Delete function  
} 
</script> 
</head> 
<body> 
<select id="mySelect"> 
<option> My bag </option> 
<option> My laptop </option> 
<option> My oil </option> 
<option> My burden </option> 
</select> 
<input type="button" name="button" value=" View the results " onclick="number();"> 
</body> 
</html>

1. Create select dynamically 


function createSelect(){ 
 
    var mySelect = document.createElement("select");  
mySelect.id = "mySelect";  
document.body.appendChild(mySelect); 
}

2. Add option option 


function addOption(){ 
 
     // According to the id Find the object,  
var obj=document.getElementById('mySelect'); 
 
      // add 1 An option  
obj.add(new   Option(" The text "," value "));  // This can only be used in IE The effective  
obj.options.add(new Option("text","value")); // This is compatible with IE with firefox 
}

3. Delete all options option 


function removeAll(){ 
var obj=document.getElementById('mySelect'); 
 
obj.options.length=0; 
 
   }

4. Delete option option 


function removeOne(){ 
var obj=document.getElementById('mySelect'); 
 
      //index, To delete the sequence number of the option, take the sequence number of the currently selected option  
 
    var index=obj.selectedIndex; 
obj.options.remove(index);  
}

5. Get the value of option option 


var obj=document.getElementById('mySelect'); 
 
var index=obj.selectedIndex; // Sequence number, the sequence number of the currently selected option  
 
var val = obj.options[index].value;

6. Get the text of the option option 


var obj=document.getElementById('mySelect'); 
 
var index=obj.selectedIndex; // Sequence number, the sequence number of the currently selected option  
 
var val = obj.options[index].text;

7. Modify option option 


var obj=document.getElementById('mySelect'); 
 
var index=obj.selectedIndex; // Sequence number, the sequence number of the currently selected option  
 
var val = obj.options[index]=new Option(" New text "," The new value ");

8. Delete select 


function removeSelect(){ 
var mySelect = document.getElementById("mySelect"); 
mySelect.parentNode.removeChild(mySelect); 
} 


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//ZH-CN" "http://www.w3.org/TR/html4/strict.dtd"> 
<html> 
<head> 
<meta http-equiv="Content-Type" content="text/html"> 
<head> 
<script language=JavaScript> 
function $(id) 
{ 
return document.getElementById(id) 
} 
 
function show() 
{ 
var selectObj=$("area") 
var myOption=document.createElement("option") 
myOption.setAttribute("value","10") 
myOption.appendChild(document.createTextNode(" Shanghai ")) 
 
var myOption1=document.createElement("option") 
myOption1.setAttribute("value","100") 
myOption1.appendChild(document.createTextNode(" nanjing ")) 
 
selectObj.appendChild(myOption) 
selectObj.appendChild(myOption1) 
 
} 
 
function choice() 
{ 
var index=$("area").selectedIndex; 
var val=$("area").options[index].getAttribute("value") 
 
if(val==10) 
{ 
var i=$("context").childNodes.length-1; 
var remobj=$("context").childNodes[i]; 
remobj.removeNode(true) 
var sh=document.createElement("select") 
sh.add(new Option(" Pudong new area ","101")) 
sh.add(new Option(" Huangpu district ","102")) 
sh.add(new Option(" Xuhui district ","103")) 
sh.add(new Option(" Putuo district ","104")) 
$("context").appendChild(sh) 
 
} 
 
if(val==100) 
{ 
var i=$("context").childNodes.length-1; 
var remobj=$("context").childNodes[i]; 
remobj.removeNode(true) 
var nj=document.createElement("select") 
nj.add(new Option(" Xuanwu borough ","201")) 
nj.add(new Option(" baixia ","202")) 
nj.add(new Option(" Xiaguan district ","203")) 
nj.add(new Option(" Qixia district ","204")) 
$("context").appendChild(nj) 
} 
} 
 
function calc() 
{ 
var x=$("context").childNodes.length-1; 
alert(x) 
 
} 
 
function remove() 
{ 
var i=$("context").childNodes.length-1; 
var remobj=$("context").childNodes[i]; 
remobj.removeNode(true) 
} 
</script> 
<body> 
 
<div id="context"> 
<select id="area" on  
change="choice()"> 
</select> 
</div> 
<input type=button value=" According to " onclick="show()"> 
<input type=button value=" Compute nodes " onclick="calc()"> 
<input type=button value=" delete " onclick="remove()"> 
</body> 
</html>

This is the end of this article, I hope you enjoy it.

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