match-like v0.1.3

match-like

match-like provides an util function to serve as an alternative to the switch statement and is inspired by Rusts match expression

Using match will make some of your code more readable and allow you to use the immutable const more frequently.

Install

npm install match-like --save

Usage

const match = require('match-like');

let returnValue = match(someValue, [
    [valueToMatch1, valueToMatch2, (value, i, all) =>
        someExpression],
    // more checks ...
    [() => defaultExpression,
]);

Parameters

• value
  Value of any type to match against.
• checks
  Array of checks. All checks will be executed in order until the first match.
  • check
    Array starting with n values and ending with a function as its last element.
    • value
      Values of any type to check against. If any of the values is equal (===) to the first value supplied to the match function, the handler will be executed. If zero values are supplied the handler will be executed in any why.
    • handler
      Callback function that will be executed if any of the values matches. The callback takes three optional arguments:
      • matchedValue The the matched element.
      • matchIndex The index of the matched value.
      • allValues Array with all values i.e. the check without the handler.

Comparison

Using match

const match = require('match-like');

const num = 7;
const what = match(num, [
    [0, 2, 4, 6, 8, () => 'an even number'],
    [1, 3, 5, 7, 9, () => 'an odd number'],
    [() => 'unknown']
]);

console.log(`${num} is ${what}`);
// => 7 is an odd number

Using switch

const num = 7;

let what;
switch (num) {
    case 0:
    case 2:
    case 4:
    case 6:
    case 8:
        what = 'an even number';
        break;
    case 1:
    case 3:
    case 5:
    case 7:
    case 9:
        what = 'an odd number';
        break;
    default:
        what = 'unknown';
}

console.log(`${num} is ${what}`);
// => 7 is an odd number

In Rust

let num = 7;
let what = match num {
    0 | 2 | 4 | 6 | 8 => "an even number",
    1 | 3 | 5 | 7 | 9 => "an odd number",
    _ => "unknown"
};

println!("{} is {}", num, what);
// => 7 is an odd number

Example

const match = require('match-like');

const now = new Date();
const day = now.getDay();

const workingDays = ['monday', 'tuesday', 'wednesday', 'thursday', 'friday'];
const weekendDays = ['saturday', 'sunday'];

function getDayName(dayNum) {
    return match(dayNum, [
        [0, () => 'sunday'],
        [1, () => 'monday'],
        [2, () => 'tuesday'],
        [3, () => 'wednesday'],
        [4, () => 'thursday'],
        [5, () => 'friday'],
        [6, () => 'saturday'],
        [() => 'not a day'],
    ]);
}

const message = match(getDayName(day), [
    [...workingDays, () => 'It\'s a working day'],
    [...weekendDays, () => 'It\'s weekend'],
]);
console.log(message);

License

This project is licensed under the terms of the MIT license. A copy of the license can be found in the root directory of the project in the file LICENSE.