domオブジェクト

1 document.getElementById(); id 

2 document.getElementsByclassName(); class 

3 document.getElementsByName(); 

4 document.getElementsByTagName(); p,h1 

1 <h1 id="aa"></h1>

2 <script>

3 var hh = document.getElementById('aa');

4 hh.innerHTML = 'bbc';

5 </script>

1 var hh = document.getElementsByTagName('h1')[0];

2 hh.innerHTML = 'ok';