Javascript control operations Daquan select (add, modify, delete, check, empty, to determine existence, etc.)

JavaScript
[1] to determine whether there select option Value = "paraValue" of Item
[2] to select the option to add a Item
[3] from the select option to delete an Item
[4] to delete selected items in select
[5] modify select option value = "paraValue" the text for "paraText"
[6] settings select Medium text = "paraText" first Item for the selected
[7] settings select Medium value = "paraValue" to select the Item
[8] has been selected select the current item of value
[9] has been selected select the current item text
[10] has been selected select the current item Index
[11] empty select items

js code

// 1.判断select选项中 是否存在Value="paraValue"的Item        
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.向select选项中 加入一个Item        
function jsAddItemToSelect(objSelect, objItemText, objItemValue) {        
    //判断是否存在        
    if (jsSelectIsExitItem(objSelect, objItemValue)) {        
        alert("该Item的Value值已经存在");        
    } else {        
        var varItem = new Option(objItemText, objItemValue);      
        objSelect.options.add(varItem);     
        alert("成功加入");     
    }        
}        

// 3.从select选项中 删除一个Item        
function jsRemoveItemFromSelect(objSelect, objItemValue) {        
    //判断是否存在        
    if (jsSelectIsExitItem(objSelect, objItemValue)) {        
        for (var i = 0; i < objSelect.options.length; i++) {        
            if (objSelect.options[i].value == objItemValue) {        
                objSelect.options.remove(i);        
                break;        
            }        
        }        
        alert("成功删除");        
    } else {        
        alert("该select中 不存在该项");        
    }        
}    

// 4.删除select中选中的项    
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.修改select选项中 value="paraValue"的text为"paraText"        
function jsUpdateItemToSelect(objSelect, objItemText, objItemValue) {        
    //判断是否存在        
    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("成功修改");        
    } else {        
        alert("该select中 不存在该项");        
    }        
}        

// 6.设置select中text="paraText"的第一个Item为选中        
function jsSelectItemByValue(objSelect, objItemText) {            
    //判断是否存在        
    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出结果        
    if (isExit) {        
        alert("成功选中");        
    } else {        
        alert("该select中 不存在该项");        
    }        
}        

// 7.设置select中value="paraValue"的Item为选中    
document.all.objSelect.value = objItemValue;    

// 8.得到select的当前选中项的value    
var currSelectValue = document.all.objSelect.value;   

// 9.得到select的当前选中项的text    
var currSelectText = document.all.objSelect.
      options[document.all.objSelect.selectedIndex].text;  

// 10.得到select的当前选中项的Index    
var currSelectIndex = document.all.objSelect.selectedIndex;    

// 11.清空select的项    
document.all.objSelect.options.length = 0;