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allfn

Summary

Returns a function that returns true if all predicates have passed when applied to its arguments.

Description

Takes one or more predicates and returns a function that takes any number of arguments and returns true if each predicate has returned logical true when applied to these arguments.

Examples

Make sure that both x and y are numbers and produce the correct answer when added up.

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const is_num = x => typeof x == 'number';

const can_answer =
 allfn( (x, y) => is_num(x) && is_num(y) // (1)
      , (x, y) => x + y === 42);         // (2)

can_answer(  40,  2); //=> true             (3)
can_answer(  20, 30); //=> false            (4)
can_answer('40',  2); //=> false            (5)

  1. 1st predicate: checks both arguments are numbers.

  2. 2nd predicate: checks numbers add up to 42.

  3. passed: both arguments are numbers and add up to 42.

  4. failed: both arguments are numbers but do not add up to 42.

  5. failed: 1st argument is not a number.

Parameters

Name Type Description
fn function One or more predicates

Return

function