Javascript 在Laravel（刀片文件）中为Jquery select设置select

我知道我可以为带有旧put文件的select标记设置select属性：

<select name="country" id="state" onChange="loadlist(this.value);" >
    <option value="usa" {{ (old('state') == 'usa') ? 'selected' : '' }}>USA</option>
    <option value="grm" {{ (old('state') == 'grm') ? 'selected' : '' }}>Germany</option>
    <option value="eng" {{ (old('state') == 'eng') ? 'selected' : '' }}>England</option>
</select>

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如何设置第二个选择标记的

{（旧（'state'）=='state name'）？'selected'：''}}

？

只需在页面加载时重新加载第二个选择：

$( document ).ready(loadlist($("select[name=country] " ). Val() ) );

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我对JavaScript还不太了解。我应该把你写在页面上的代码放在哪里？在标签里？

function loadlist(country){
with(document.getElementById('state')) 
    {
        options.length = 0;

    if(country == ''){
        options[0] = new Option('Select country' , '');
    }
    if (country == 'usa') {
        options[0] = new Option('Select' , '');
        options[1] = new Option('NewYork' , 'NewYork');
        options[2] = new Option('Florida' , 'Florida');
        options[3] = new Option('California' , 'California');
    }
    if (country == 'grm') {
        options[0] = new Option('Select' , '');
        options[1] = new Option('Bayern' , 'Bayern');
        options[2] = new Option('Hamburg‎' , 'Hamburg‎');
        options[3] = new Option('Berlin' , 'Berlin');
    }
    if (country == 'eng') {
        options[0] = new Option('Select' , '');
        options[1] = new Option('Buckingham' , 'Buckingham');
        options[2] = new Option('Cambridge‎' , 'Cambridge‎');
        options[3] = new Option('London' , 'London');
    }
}
}

$( document ).ready(loadlist($("select[name=country] " ). Val() ) );