The Zend Developer Zone has pointed out several code snippets from Kevin van Zonneveld that are ports of some favorites from the world of PHP over to Javascript.
They're broken up into a series of posts to his blog and include:
Each post includes a description, the parameters the function takes in, return values, credits for the code and the Javascript code to make it work. For a library with the complete list of ported functions, you can download this .js file (or the compressed version).
You can check out the full list of ported functions in this category on his blog.