将光标定位在text,textarea最后的步骤

var setpos = function(o){ 
  if (o.setSelectionRange) { 
      setTimeout(function(){
      o.setSelectionRange(o.value.length, o.value.length);  
      o.focus()} ,0) 
  }else if (o.createTextRange) {
    var textrange=o.createTextRange();
    textrange.moveStart("character",o.value.length);
    textrange.moveEnd("character",0);
    textrange.select();
  }
  
};