> 
> **Possible Duplicate:**  
> 
> [How can I detect if Flash is installed and if not, display a hidden div that informs the user?](https://stackoverflow.com/questions/998245/how-can-i-detect-if-flash-is-installed-and-if-not-display-a-hidden-div-that-inf) 
> 
> 
> 

so:

```
var _isflash = navigator.plugins['Shockwave Flash'];  
if(_isflash == "undefined")
{
  console.log("not exists flash")
}
else
{
  console.log("flash!") 
}

```

why this not work?

```
document.write(_isflash) // undefined

```

if flash off, \_isflash = undefined...
please help me