h5p-lib-controls/src/scripts/utils/functional.js

Library for adding user input to web applications

/**
 * Returns a curried version of a function
 *
 * @param {function} fn
 *
 * @public
 *
 * @return {function}
 */
export const curry = function(fn) {
  const arity = fn.length;

  return function f1() {
    const args = Array.prototype.slice.call(arguments, 0);
    if (args.length >= arity) {
      return fn.apply(null, args);
    }
    else {
      return function f2() {
        const args2 = Array.prototype.slice.call(arguments, 0);
        return f1.apply(null, args.concat(args2));
      }
    }
  };
};

/**
 * Compose functions together, executing from right to left
 *
 * @param {function...} fns
 *
 * @function
 * @public
 *
 * @return {function}
 */
export const compose = (...fns) => fns.reduce((f, g) => (...args) => f(g(...args)));

/**
 * Applies a function to each element in an array
 *
 * @param {function} fn
 * @param {Array} arr
 *
 * @function
 * @public
 *
 * @return {function}
 */
export const forEach = curry(function (fn, arr) {
  arr.forEach(fn);
});

/**
 * Maps a function to an array
 *
 * @param {function} fn
 * @param {Array} arr
 *
 * @function
 * @public
 *
 * @return {function}
 */
export const map = curry(function (fn, arr) {
  return arr.map(fn);
});

/**
 * Applies a filter to an array
 *
 * @param {function} fn
 * @param {Array} arr
 *
 * @function
 * @public
 *
 * @return {function}
 */
export const filter = curry(function (fn, arr) {
  return arr.filter(fn);
});

/**
 * Applies a some to an array
 *
 * @param {function} fn
 * @param {Array} arr
 *
 * @function
 * @public
 *
 * @return {function}
 */
export const some = curry(function (fn, arr) {
  return arr.some(fn);
});

/**
 * Returns true if an array contains a value
 *
 * @param {*} value
 * @param {Array} arr
 *
 * @function
 * @public
 *
 * @return {function}
 */
export const contains = curry(function (value, arr) {
  return arr.indexOf(value) != -1;
});

/**
 * Returns an array without the supplied values
 *
 * @param {Array} values
 * @param {Array} arr
 *
 * @function
 * @public
 *
 * @return {function}
 */
export const without = curry(function (values, arr) {
  return filter(value => !contains(value, values), arr)
});

/**
 * Takes a string that is either 'true' or 'false' and returns the opposite
 *
 * @param {string} bool
 *
 * @public
 * @return {string}
 */
export const inverseBooleanString = function (bool) {
  return (bool !== 'true').toString();
};