js动态修改css样式以及修改类名

function  updateStyle(){
var obj = document.getElementById('name');
obj.style.width = "200px"
}

function updateStyle() {
   var obj = document.getElementById("name");
   obj.style.cssText = "background-color:black; display:block;color:White;width:200px";
 
}

function updateStyle() {
   var obj = document.getElementById("name");
   obj.style.setProperty('width','250px');
 
}

function updateStyle() {
  var obj = document.getElementById("name");
  //obj.className = "name1";
  obj.setAttribute("class", "name1");
}