//html
<div class="divClass" id="divId" ></div>

//js
window.onload = function(){
 var divId = document.getElementById('divId');
 console.log(divId.attributes);
}

console.log(divId.attributes[0]); //打印 class="divClass"
console.log(divId.attributes.class) //打印 class="divClass"

console.log(divId.getAttribute('class')) //打印divClass
console.log(divId.getAttribute('id')) //打印divId

<div class="divClass" id="divId" addUserDefine="zidingyi"></div>

console.log(divId.class);  //打印 divClass
console.log(divId.addUserDefine) //打印 undefined

var obj = {};
Object.defineProperty(obj,'name',{
 value:'Property'
})

console.log(obj.name) //打印 Property

//html
<input value="initValue" id="ipt"/>

//js
window.onload = function(){
 var ipt = document.getElementById('ipt');

 ipt.value = 'changeValue'
 console.log(ipt.value);
 console.log(ipt.getAttribute('value'));
}

console.log(ipt.value);   //changeValue
console.log(ipt.getAttribute('value'));  //initValue

//html
<input value="initValue" id="ipt"/>

//js
window.onload = function(){
 var ipt = document.getElementById('ipt');

 ipt.setAttribute('value','changeValue')
 console.log(ipt.value);
 console.log(ipt.getAttribute('value'));

}

console.log(ipt.value);   //changeValue
console.log(ipt.getAttribute('value'));  //changeValue

//js
var obj = {
 value : false,
}

var ipt = document.getElementById('ipt');

obj.value = true;  //property更改
ipt.setAttribute('value',true) //attribute更改

console.log(typeof obj.value); //boolean
console.log(obj.value)   //true

console.log(typeof ipt.value) //string
console.log(ipt.value);   //true