Useful utilities to manipulate functions

funcUtils.js

/**
 * Composes a function that returns the result of invoking the given functions
 * with the `this` binding of the created function, where each successive
 * invocation is supplied the return value of the previous.
 **/

export function pipe(...funcs) {
  const length = funcs.length;
  let index = length;
  while (index--) {
    if (typeof funcs[index] !== 'function') {
      throw new TypeError('Expected a function');
    }
  }
  return function(...args) {
    let index = 0;
    let result = length ? funcs[index].apply(this, args) : args[0];
    while (++index < length) {
      result = funcs[index].call(this, result);
    }
    return result;
  };
}

export function compose(...funcs) {
  return pipe(...funcs.reverse());
}