Swap two elements in an array. Easy, peasy.

Install

$ npm install swapsy

Example

const swapsy = require('swapsy');

const arr = [ 'hello', 'world' ]
const fromIndex = 0
const toIndex = 1

swapsy(arr, fromIndex, toIndex)

// Returns [ 'world', 'hello' ]

Why?

• ✅ Tiny (~400 bytes)
• ✅ Zero-Dependencies
• ✅ Immutable/Pure
• ✅ ES6
• ✅ Tested

Better Example

Suppose you use React and Redux, and you have some kind of action and a reducer that reorders some components for the user.

Your action might look like this:

const swapItems = (from, to) => {
  return {
    type: 'SWAP_ITEMS',
    from,
    to
  }
}

And your reducer might have looked like this:

const items = (state = [], ({ from, to })) => {
  switch (action.type) {
    case 'SWAP_ITEMS':
      const x = state[from];
      const y = state[to];
      state[to] = x;
      state[from] = y;
      return state;
  }
}

Which is bad because it's long, ungainly, wasteful and mutates the state directly. Also note, there are worse implementations than the one above.

But with swapsy, keep your reducers pure and readable:

const swap = require('swapsy');

const items = (state = [], ({ from, to })) => {
  switch (action.type) {
    case 'SWAP_ITEMS':
      return swap(state, from, to);
  }
}