Finding a string in another string

Using actionscript, how do I find if the following string contains the substring assets/Wallpaper?

http://virtual.c7beta.com/assets/Wallpaper/default.jp&session_id=1fb764b01a2843763a76316a6开发者_JAVA技巧c85313a

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indexOf is your friend. It tells you the first occurence of a string in another string ( and even if there is none. )