Useful utility functions I've come up with, found or seen during my career.

arrayWithNumbers.js

/**
 * Accepts a number and returns an Array filled with numbers
 * starting from 1 and up to the given number.
 * @example
 * arrayWithNumbers(5)
 * // [1, 2, 3, 4, 5]
 */
export default function arrayWithNumbers(number) {
  return Array(number).fill().map((_, i) => i + 1)
}

compose.js

function compose(...funcs) {
  return funcs.reduce((f, g) => (...args) => f(g(...args)))
}

getObjectLeaves.js

import * as R from 'ramda'

/**
 * Returns the leaves of the given Object.
 * @param {Object} object
 * @returns {any[]}
 * @example
 * getObjectLeaves({ a: 2, b: { c: 3 })
 * // [2, 3]
 */
const getObjectLeaves = R.when(
  R.is(Object),
  R.compose(
    // note that partial application doesn't seem to work here
    (vals) => R.chain(getObjectLeaves, vals),
    R.values,
  ),
)

export default getObjectLeaves

interpolate.js

/**
 * Interpolates the given string with the given params.
 * @param {string} string
 * @param {Object} params
 * @returns {string}
 *
 * @example
 * interpolate('/user/{userId}/{messageId}', { userId: 5, messageId: 92 })
 * // "/user/5/92"
 */
function interpolate(string, params) {
  return string.replace(/{(\w+)}/g, (_, paramName) => params[paramName])
}

isset.js

/**
 * Determines the existance of the provided variable.
 * @param {any} variable
 * @returns {Boolean}
 */
export default function isset(variable) {
  return (typeof variable !== 'undefined') && (variable !== null);
}

to.js

/**
 * Returns a tuple of data and error for the given promise.
 * Useful for error handling of promises with async/await.
 * @param {Promise} promise
 * @returns {Promise}
 * @example
 * const [data, error] = await to(getProducts())
 */
export default function to(promise) {
  return promise
    .then((data) => [data])
    .catch((error) => [null, error])
}