UserAgent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/50.0.2661.102 Safari/537.36

Steps to reproduce the problem:
1.  A javascript function --
               function testprompt() {var pw=prompt("Enter password:" ,"");}
2. Called from a .php page being tested on WIndows7 localhost (IIS).
3. When the .php file has parameters, such as --
               http://localhost/index.php?ws=0
4. An error is seen in the Chrome debugger --
               script.js:41 Uncaught TypeError: prompt is not a function
5. Yet when the same .php is loaded without parameters --
               http://localhost/index.php
6. There is no error.
7. Also no error, with or without parameters, when run on a remote (Apache) server.
8  No error in Firefox or IE11 browsers.

Any clue what gives?

What is the expected behavior?
window.prompt() should work.  it fails only in a .php file on Windows 7 localhost where the .php was passed a parameter.

What went wrong?
window.prompt() in javascript code throws error "Uncaught TypeError: prompt is not a function" seen in Chrome debugger 

Did this work before? N/A 

Chrome version: 50.0.2661.102  Channel: stable
OS Version: 6.1 (Windows 7, Windows Server 2008 R2)
Flash Version: Shockwave Flash 21.0 r0

code works in Firefox and IE 11.