SOURCE

function my() {
  document.getElementById('h1').style.color = 'red';
}
function my_1() {
  var val = document.getElementById('input').value;
  if (val == '') {
    alert('请输入内容');

  } else if (isNaN(val)) {
    alert('输入的不是数字');
  }
}
function my2(){
  document.getElementById('p3').innerHTML='新数据';
}
var str =" ddd";
document.write( str.toUpperCase());
}
var obj={
  first : "111",
  second : '222',
  third : '333'
};
document.write(obj.first+'<br/>');
person=new Object();
person.name="Tom";
person.sex="male";
person.age="22";
document.write(person.name+' is a '+ person.age+" "+ person.sex);

<div>
  <h1 id="h1">
    js入门
  </h1>
  <button id="btn" class="btn" onclick="my()">
    click
  </button>
</div>
<div>
  <input type="text" id="input" />
  <button onclick="my_1()">
    click
  </button>
</div>
<div>
  <p id='p3'>原数据</p>
  <button onclick="my2()">click</button>
</div>
<div>
  <p>toUpperCase转大写</p>
  <p id="pp">hello world</p>
  <p id="p4"></p>
  <button onclick=my3()>click</button>
</div>