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JavaScript operations on HTML drop-down list tags

巴扎黑

Sep 08, 2017 am 11:25 AM

html javascript js

先给大家讲下大概实现思路，具体内容介绍请看下面。

判断select选项中是否存在Value="paraValue"的Item

向select选项中加入一个Item

从select选项中删除一个Item

删除select中选中的项

修改select选项中 value="paraValue"的text为"paraText"

设置select中text="paraText"的第一个Item为选中

设置select中value="paraValue"的Item为选中

得到select的当前选中项的value

得到select的当前选中项的text

得到select的当前选中项的Index

清空select的项

js 代码

// 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 &lt; objSelect.options.length; i++) {    
    if (objSelect.options[i].value == objItemValue) {    
      isExit =true;    
      break;    
    }    
  }    
  return isExit;    
}

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// 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");   
  }    
}

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// 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 &lt; 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");    
  }    
}

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// 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;  
    }  
  }  
}

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// 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 &lt; 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");    
  }    
}

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// 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 &lt; 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");    
  }    
}

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// 7.设置select中value="paraValue"的Item为选中

1	`document.all.objSelect.value = objItemValue;`

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// 8.得到select的当前选中项的value

1	`var` `currSelectValue = document.all.objSelect.value;`

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// 9.得到select的当前选中项的text

1	`var` `currSelectText = document.all.objSelect.options[document.all.objSelect.selectedIndex].text;`

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// 10.得到select的当前选中项的Index

1	`var` `currSelectIndex = document.all.objSelect.selectedIndex;`

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// 11.清空select的项

1	`document.all.objSelect.options.length =0;`

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