checking for specific type / class in Javascript

is_type_x.js

// - check type of input
is_type_x = function(object, type){

// go through cases: undefined, object, primitive
if( typeof(object) === "undefined" ){ 
// undefined cannot be matched 
return false;
} else if( typeof(object) === "object" ){ 
// objects have to be matched against constructor
if( window[type] === undefined ){
return false;
}else{
return ( object instanceof eval(type) );
}
} else if( 
// everything not an object has to match againt its type
$.inArray(
    typeof(object), 
    ["number", "boolean", "string", "symbol", "function"]
) >= 0
){
if ( typeof(object) === type ){
return true;
}else{
return false;
}
}

// if those checks do not catch, return false
return false;
};