JS检测对像(支持多版本)

function myFunc(elemID){
  var obj
  if(document.all){
    obj=document.all(elemID)
  }else if(document.getElementById){
    obj=document.getElementById(elemID)
  }else if(document.layers){
    obj=document.layers[elemID]
  }
  if(obj){
    //statements that work on the object
  }
}