JavaScript implementation method to determine variable type based on custom function-JS Tutorial-php.cn

JavaScript implementation method to determine variable type based on custom function

高洛峰

Release： 2016-12-05 14:41:38

Original

1729 people have browsed it

The example in this article describes the implementation method of JavaScript to determine the variable type based on a custom function. Share it with everyone for your reference, the details are as follows:

Typeof is usually used to determine the type of js variables, but many times typeof alone cannot meet the requirements.

I wrote a custom function to do this, and the judgment is more comprehensive.

function varType(v){
 if ( typeof v=== "object" ){
  if (v=== null ) return &#39;null&#39; ;
  if (v. constructor )
   return (v. constructor .toString()).match(/(?: )[/w/$]+/)[ 0 ];
  if ( typeof typeof2=== &#39;undefined&#39; && window .execScript){
   window .execScript( &#39;Function vbsTypeName(o):vbsTypeName=TypeName(o):End Function&#39; , &#39;vbscript&#39; );
   window .execScript( &#39;function typeof2(o){return vbsTypeName(o)}&#39; , &#39;jscript&#39; );
  }
  if ( typeof typeof2!== &#39;undefined&#39; ){
   return typeof2(v);
  }
  return "object" ;
 }
 return typeof v;
}
//对于普通js常量和js对象，各浏览器是基本一致的
alert (varType()); //undefined
alert (varType( 100 )); //number
alert (varType({})); //Object
alert (varType([])); //Array
alert (varType(/ /)); //RegExp
alert (varType( new Date ())); //Date
alert (varType( Date )); //function
alert (varType( Object )); //function
alert (varType( RegExp )); //function
//对于DOM对象，各浏览器可能会有不同值
alert (varType( window )); //IE:HTMLWindow2 FF:Window
alert (varType( document )); //IE:HTMLDocument FF:HTMLDocument
alert (varType( document .body)); //IE:HTMLBody FF:HTMLBodyElement
alert (varType( Option )); //IE:Object FF:function
alert (varType( Image )); //IE:Object FF:function
alert (varType( navigator )); //IE:DispHTMLNavigator FF:Navigator
//以下几个只适用于IE，其他内核浏览器不支持
alert (varType( ActiveXObject )); //IE:function
alert (varType( Enumerator )); //IE:function
alert (varType( new ActiveXObject ( "Scripting.Dictionary" ))); //IE:Dictionary
alert (varType( new Enumerator ())); //IE:Enumerator

Copy after login