JavaScript Select Add, modify, delete, select, empty, and judge existing functions

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JS Code 1. Determine if there is a value= "Paravalue" Item in the Select option function Jsselectisexititem (Objselect, Objitemvalue) { var isexit = false; for (var i = 0; I < objSelect.options.length; i++) { if (Objselect.options[i].value = = Objitemvalue) { Isexit = true; Break } } return isexit; } //2. Add an item function to the Select option Jsadditemtoselect (Objselect, Objitemtext, objitemvalue) {     //Determine if there is a     if (Jsselectisexititem (Objselect, Objitemvalue)) {          alert ("The value of the item already exists");    } else {         var varitem = new Option (Objitemtext, obj Itemvalue);         ObjSelect.options.add (varitem);         alert ("Join successfully");    } }        //3. Remove one item function Jsremoveitemfromselect (Objselect, Objitemvalue) from the Select option {    // To determine if there is a     if (Jsselectisexititem (Objselect, Objitemvalue)) {          for (var i = 0; I < objSelect.options.length i++) {        &N bsp;    if (Objselect.options[i].value = = objitemvalue) {                  ObjSelect.options.remove (i);                 break;            }        }         Alert ("Successful deletion");    } else {         alert ("This item does not exist in this select");     } }    4. Delete selected items in select function Jsremoveselecteditemfromselect (objselect) { var length = objselect.options.length-1; for (var i = length; I >= 0; i--) { if (objselect[i].selected = = True) { Objselect.options[i] = null; } } } 5. Modify the Select option Value= "Paravalue" text is "Paratext" function Jsupdateitemtoselect (Objselect, Objitemtext, Objitemvalue) { To determine whether there is if (Jsselectisexititem (Objselect, Objitemvalue)) { for (var i = 0; I < objSelect.options.length; i++) { if (Objselect.options[i].value = = Objitemvalue) { Objselect.options[i].text = Objitemtext; Break } } Alert ("Successful modification"); } else { Alert ("The item does not exist in the select"); } } 6. Set the first item of text= "Paratext" in Select to select function Jsselectitembyvalue (Objselect, Objitemtext) { To determine whether there is var isexit = false; for (var i = 0; I < objSelect.options.length; i++) { if (Objselect.options[i].text = = Objitemtext) { Objselect.options[i].selected = true; Isexit = true; Break } } Show the results if (isexit) { Alert ("Successfully selected"); } else { Alert ("The item does not exist in the select"); } } 7. Set the item of value= "Paravalue" in Select to select Document.all.objSelect.value = Objitemvalue; 8. Get the Value,index,text of the current selected item function GetValue (obj) { return obj.value; } 9. Get the index of the currently selected item function GetIndex (obj) { return obj.selectedindex; } 10. Get the text of the currently selected item function GetText (obj) { return obj.options[obj.selectedindex].text; } 11. Clear all options function Clear (obj) { obj.options.length = 0; }

1, to determine if there is a value= "Paravalue" Item
2 in the Select option, add an item
3 to the Select option, delete an item from the Select Option
4, and delete the selected item from the Select
5, modify the Select option Value= "Paravalue" text is "Paratext"
6, set the first item in the Select Text= "Paratext" to select
7, Set the item for value= "Paravalue" in Select to select
8, get the value of the current selected item for select
9, get the text
10 of the currently selected item for select, Gets the index
11 of the currently selected item for select, empties the Select item