How can you execute javascript on QTP/UFT??

First we have to go this link 

HKEY_LOCAL_MACHINE\SOFTWARE\Mercury Interactive\QuickTest Professional\Configuration_UI\ScriptMgr

Create a new String value with name AltProgID and value "Mercury.JSScriptMgr" and change the value of "Create" to 1

Create a new child key inside the key
HKEY_LOCAL_MACHINE\SOFTWARE\Mercury Interactive\QuickTest Professional\Configuration_UI\ScriptConstants
{0ECD5785-BE7D-11d4-8EAF-11135659EC56}

Repeat the same steps for the below key
HKEY_LOCAL_MACHINE\SOFTWARE\Mercury Interactive\QuickTest Professional\Configuration

Open
C:\Program Files\Mercury Interactive\QuickTest Professional\bin\QTEditor.ini
Add the below parameter to [General options]
AllowJavaScript = 1
DisableVBScript = 1