treis

treɪs | a simple tool to debug and observe functions

treis will answer the question "what arguments is this function called with and what does it return?".

It can be particularly useful when programming in point-free style.

If you want to know what a function does in the middle of a compose pipeline, just do:

compose(h, treis(g), f);

install

$ npm install treis

usage

treis(label?, Function) → Function

Returns a decorated version of fn that prints the arguments given to fn and its return value.

You can optionally label functions by passing a name before the function to be decorated, if not, treis will try to use fn.name.

Writes output to stderr.

example

const R = require('ramda');
const treis = require('treis');
 
//    greet ∷ String → String
const greet = (name) =>
  `Hello, ${name}!`
 
//    greetPeople ∷ [String] → String
const greetPeople =
  R.compose(R.join('\n'),
            R.map(treis(greet)));
 
const people = ['John', 'Jill', 'Bruce'];
console.log(treis(greetPeople)(people));

output

browser support

Works with browserify.

useful vim mappings

These require surround.vim:

" Surround a word with treis()
nmap <buffer> <Leader>tr ysiwftreis<CR>f(
 
" Surround a visual selection with treis()
vmap <buffer> <Leader>tr Sftreis<CR>f(
 
nmap <buffer> <Leader>tR ysiwfrequire('treis')<CR>f(
vmap <buffer> <Leader>tR Sfrequire('treis')<CR>f(