avocado-old/packages/core/function.js

/**
 * Composes single-argument functions from right to left. The rightmost
 * function can take multiple arguments as it provides the signature for
 * the resulting composite function.
 *
 * @param {...Function} funcs The functions to compose.
 * @returns {Function} A function obtained by composing the argument functions
 * from right to left. For example, compose(f, g, h) is identical to doing
 * (...args) => f(g(h(...args))).
 */
export function compose(...funcs) {
  if (funcs.length === 0) {
    return arg => arg;
  }
  if (funcs.length === 1) {
    return funcs[0];
  }
  return funcs.reduce((a, b) => (...args) => a(b(...args)));
}

export function fastApply(holder, fn, args) {
  if (holder || args.length > 5) {
    return fn.apply(holder, args);
  }
  if (0 === args.length) {
    return fn();
  }
  if (1 === args.length) {
    return fn(args[0]);
  }
  if (2 === args.length) {
    return fn(args[0], args[1]);
  }
  if (3 === args.length) {
    return fn(args[0], args[1], args[2]);
  }
  if (4 === args.length) {
    return fn(args[0], args[1], args[2], args[3]);
  }
  if (5 === args.length) {
    return fn(args[0], args[1], args[2], args[3], args[4]);
  }
}