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function preventDupes(select, index) {
var options = select.options,
len = options.length;
while(len--) {
options[ len ].disabled = false;
}
select.options[ index ].disabled = true;
if(index === select.selectedIndex) {
alert('You\'ve already selected the item "' + select.options[index].text + '".\n\nPlease choose another.');
this.selectedIndex = 0;
}
}
var select1 = select = document.getElementById('select1');
var select2 = select = document.getElementById('select2');
var select3 = select = document.getElementById('select3');
var select4 = select = document.getElementById('select4');
var select5 = select = document.getElementById('select5');
select1.onchange = function() {
preventDupes.call(this, select2, this.selectedIndex);
preventDupes.call(this, select3, this.selectedIndex);
preventDupes.call(this, select4, this.selectedIndex);
preventDupes.call(this, select5, this.selectedIndex);
};
select2.onchange = function() {
preventDupes.call(this, select1, this.selectedIndex);
preventDupes.call(this, select3, this.selectedIndex);
preventDupes.call(this, select4, this.selectedIndex);
preventDupes.call(this, select5, this.selectedIndex);
};
select3.onchange = function() {
preventDupes.call(this, select1, this.selectedIndex);
preventDupes.call(this, select2, this.selectedIndex);
preventDupes.call(this, select4, this.selectedIndex);
preventDupes.call(this, select5, this.selectedIndex);
};
select4.onchange = function() {
preventDupes.call(this, select1, this.selectedIndex);
preventDupes.call(this, select2, this.selectedIndex);
preventDupes.call(this, select3, this.selectedIndex);
preventDupes.call(this, select5, this.selectedIndex);
};
select5.onchange = function() {
preventDupes.call(this, select1, this.selectedIndex);
preventDupes.call(this, select2, this.selectedIndex);
preventDupes.call(this, select3, this.selectedIndex);
preventDupes.call(this, select4, this.selectedIndex);
};
我试图禁用已经选择的下拉字段,但是它禁用了最后选择的下拉值。我想要的是什么;如何在使用Javascript禁用下列下拉菜单中选择值
当用户第一次选择会计时,应该在其他4个下拉列表中禁用该选项。然后如果用户选择生物学,则生物学和会计必须在其他3个下拉列表中禁用。因此,用户可以设置前五个选项