js设置select下拉菜单栏随机显示默认值

<select id="selID"> 
    <option value="0" selected>下拉菜单一</option> 
    <option value="1">下拉菜单二</option> 
    <option value="2">下拉菜单三</option> 
    <option value="3">下拉菜单四</option>
    <option value="4">下拉菜单五</option>  
</select>

var sel = document.getElementById('selID')
var opt = sel.querySelectorAll('option')

var dt = ['一','二','三','四','五','六','七']
var xz = '下拉菜单' + dt[Math.floor(Math.random() * (opt.length - 0 + 1)) + 0]
for(var i=0;i<opt.length;i++) {

    if(opt[i].innerText == xz) {
        opt[i].selected = true
    } else {
        opt[i].selected = false
    }
}
console.log(xz,opt);