list-to-hash

Create a hash Object with keys from an Array

Installation

Install the module with the following command:

npm install --save list-to-hash

Usage

1var listToHash = require('list-to-hash');
2
3var keys = [
4  'apples',
5  'bananas',
6  'oranges',
7  'strawberries'
8];
9
10/**
11 * @param {(Array|function}} keys
12 * @param {(any|function)} value
13 * @returns {Object}
14*/
15listToHash(keys, 'delicous!');

Will output the following:

1{
2  'apples': 'delicious!',
3  'bananas': 'delicious!',
4  'oranges': 'delicious!',
5  'strawberries': 'delicious!'
6}

Dynamic Keys / Values

If you pass a function to either of the arguments, it will be invoked for each item expecting you to calculate a return value.

Dynamic Keys

If your values is a function, it will be called with the following signature:

1function calculateValue(value, index, array) {
2  return 'some string here';
3}

Example

1const values = [
2  {id: 'hello'},
3  {id: 'world'},
4  {id: 'foo'}
5]
6const pluckId = (value, index, array) => value.id + '_' + index;
7
8listToHash(pluckId, values)
9
10// will return the following:
11{
12  'hello_0': {id: 'hello'},
13  'world_1': {id: 'world'},
14  'foo_2': {id: 'foo'}
15}

Dynamic Values

If your values is a function, it will be called with the following signature:

1function calculateValue(key, index, array) {
2  return 'some string here';
3}

Example

1const keys = [
2  'apples',
3  'bananas',
4  'oranges',
5  'strawberries'
6];
7
8const reverse = input => input.split.reverse();
9
10listToHash(keys, reverse)
11
12// will return the following:
13{
14  'apples': 'selppa',
15  'bananas': 'sananab',
16  'oranges': 'segnaro',
17  'strawberries': 'seirrebwarts'
18}

Edge Cases

If you have a list of keys and the values should all be a particular function, like so:

1const keys = ['a', 'b', 'c'];
2function yourOwnFn() { doSomething(); }
3
4listToHash(keys, yourOwnFn);

This will not point the keys a, b and c to yourOwnFn, because it treats yourOwnFn as the dynamic value calculator and expects it to return the actual value you want.

To work around this, make the return value of the value calculator function be the actual function you want it to point to like so:

1const keys = ['a', 'b', 'c'];
2function yourOwnFn() { doSomething(); }
3const getYourOwnFn = (key, index, array) => { return yourOwnFn; }
4
5listToHash(keys, getYourOwnFn);

This usage will give you the results you expect.

Testing

To run the test, cd into the folder and run npm test.