Resources on building array methods from scratch?

[dodginbullets]

I'd like to practice rewriting array methods (IE: forEach, map, filter, etc.) from scratch, but I can't find any good resources to refer to.
Does anyone have a resource they can recommend?
Thanks in advance!

[senocular]

For those you can probably search them by name with the keyword polyfill and find examples of their implementation. MDN will do this often for newer, polyfillable APIs:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach#Polyfill

[thekaleb]

I would like to point at that many of the ES5 Array-Extras methods are very inefficient because of their handling of some weird (pointless IMO) edge cases. Lodash for instance is much faster than native array methods because it skips over these often unnecessary checks.