在页面加载时运行javascript for dropdown？

Question

我有一个js函数,可以在更改时控制select元素的外观.但是,我需要的一件事是代码从start开始运行,这样当元素加载选定的选项时,应该已经应用了类.

CSS:

  select {height: 50px; width: 80px; border: solid 1px #c8c8c8; color:rgba(0, 0, 0, 0);}
select:focus, #select:focus {
  color:black;
}

.lightgrey {background: lightgrey}
.green {background:green}
.orange {background:orange}
.yellow {background:yellow}
.red {background:red}
.purple {background:purple}

JavaScript的:

function colourFunction(select) {
        var colour = select.options[select.selectedIndex].className;

        select.className = colour;
        select.blur();
    }

选择:

<select class="selectElement" runat="server" id="dropdown_" onchange="colourFunction(this)">
                    <option selected="selected" class="lightgrey" value="N">N</option>
                    <option class="green" value="G">G</option>
                    <option class="orange" value="O">O</option>
                    <option class="yellow" value="A">A</option>
                    <option class="red" value="R">R</option>
                    <option class="purple" value="U">U</option>
                </select>

我希望N的类在加载时应用颜色:rgba(0,0,0,0);

Answer 1

如果你使用jquery：

$(function(){
 //all onload actions you want
});

如果你想坚持使用纯js

document.onreadystatechange=function(){
//all onload actions you want
}