js input hidden get value

1console.log(document.getElementById('abcId').value);

1document.getElementById("myHiddenInputID").value = "MyNewValue";

1// HTML : 
2<input type=hidden id="abcId" name="abcName" value="Wall Street! Money Never Sleep"/>
3  
4  // JAVASCRIPT :
5   alert(document.getElementById('abcId').value);
6   alert(document.formName.elements['abcName'].value);