SOURCE

var input=document.getElementById('usr');
input.value;//获取值；
input.value='olleher';//设置值；
document.getElementById('psw1').value='147852';

//click事件提交表单
function dosubmit(){
  var subtext=document.getElementById('psw1');
  subtext.submit();
}

<form>
  usrname:<input type='text' id='usr'><br><br>
  password:<input type='password' id='psw1'><br><br>
  <input type='submit' onclick='dosubmit()' id='submit' value='提交'>
</form><br>
<p title='世界卫生组织'>W H O</p>
<div>
  <h3>获取值、设置值</h3>
  <p>可以直接运用value属性获取/设置值；</p>
  <p>用submit()方法提交表单；</p>
</div>

form{
  border:1px solid red;
  width:60%;
  margin:0;
  padding:30px 15px;
  position:relative;
  left:20%;
  top:20px;
  color:orange;
  background-color:gray;
}