fbranches

fbranches

A functional version of javascript's switch and if statements (beware of the f prefix).

if statement

if(k==k1) { return v1 }
else { return v2 }

becomes

import { fif } from 'fbranches'
fif(k1)
  .fthen(v1)
  .felse(v2)
  .exec(k)

or

import { fif } from 'fbranches'
fif()
  .fthen(v1)
  .felse(v2)
  .exec(k==k1)

or

import { fif } from 'fbranches'
fif(k==k1)
  .then(v1)
  .else(v2)
  .eval()

(beware: this command uses eval instead of exec).

switch statement

switch(k) {
  case k1:
  	return v1;
  case k2:
    return v2;
  default:
    return v3
}

becomes

import { fswitch } from 'fbranches'
fswitch()
  .fcase(k1, v1)
  .fcase(k2, v2)
  .fdefault(v2)
  .exec(k)

or

import { fswitch } from 'fbranches'
fswitch(k)
  .case(k1, v1)
  .case(k2, v2)
  .default(v2)
  .eval()

Beware: when the condition is specified in the fswitch() call, we use the eval function, not exec (see the section about the smart variants for more information about case and default).

The fswitch statement can also be used without head value (since version 1.4):

import { fswitch } from 'fbranches'
fswitch()
  .case(some_condition, v1)
  .case(some_other_condition, v2)
  .default(v3)
  .eval()

Function variants

All fthen, felse, fcase and fdefault have a variant, postfixed by _f, that accept a function instead of v. The arguments to the function may be passed in the exec function.

For example, with fif:

import { fif } from 'fbranches'
fif(k1)
  .fthen_f(f1)
  .felse(v2)
  .exec(k, a1, a2)

The exec function would call f1(a1, a2) if k==k1, or return v2 otherwise.

Smart variants

The fswitch function's return object also defines the functions case and default, that smartly dispatch between fcase_f and fcase if the second parameter is a function or not. Note that if you need to use fswitch to dispatch between function values, you must use fcase.

The same, the fif function's return object also defines the functions then and else.