maccha

Pattern matching for js

About name

maccha - fine powder tea. As in case of tea, you could make the pattern fine powder for matching. Also "maccha" (matcha) sounds similarly with "matching"

Short description

Matchable value could be:

• primitive or wrapper object of primitive
• array ([1,2,3] or new Array(1,2,3))
• struct ({a:1, b:2, c:"3"})
• instance of user class
• composition entity of last three cases

match takes matchable value and returns a function which takes a sequence of ca$e's.

Each of ca$e takes the pattern as first argument and rest sequence of arguments are guards (additional predicates of matchable value). ca$e returns a function which takes a callback function - it be execute if matching would be successful. ca$e matching execute one by one up to down.

el$e - just default action if none of ca$e's will be successful. If el$e is absent and there is no any successful matching it throws Error.

ANY is just a constant a-la wildcart.

TAIL is another constant. It uses for tail of array for pattern.

Example

match({x:1,y: {z: 2}})(
    ca$e({x:1, y:2, z: ANY}, (obj => obj.z > 10))(obj => "struct with x, y, z and z is more than 10"),
    ca$e([1, 2, TAIL])(arr => "1,2,.... and something else"),
    ca$e({x:1, y: {z: 2}})(obj => "It's very complex object"),
    el$e(any => `It something different`)
)

// "It's very complex object"