lodash/lodash.flow/index.js

/**
 * lodash (Custom Build) <https://lodash.com/>
 * Build: `lodash modularize exports="npm" -o ./`
 * Copyright jQuery Foundation and other contributors <https://jquery.org/>
 * Released under MIT license <https://lodash.com/license>
 * Based on Underscore.js 1.8.3 <http://underscorejs.org/LICENSE>
 * Copyright Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
 */
var baseFlatten = require('lodash._baseflatten'),
    rest = require('lodash.rest');

/** Used as the `TypeError` message for "Functions" methods. */
var FUNC_ERROR_TEXT = 'Expected a function';

/**
 * Creates a `_.flow` or `_.flowRight` function.
 *
 * @private
 * @param {boolean} [fromRight] Specify iterating from right to left.
 * @returns {Function} Returns the new flow function.
 */
function createFlow(fromRight) {
  return rest(function(funcs) {
    funcs = baseFlatten(funcs, 1);

    var length = funcs.length,
        index = length;

    if (fromRight) {
      funcs.reverse();
    }
    while (index--) {
      if (typeof funcs[index] != 'function') {
        throw new TypeError(FUNC_ERROR_TEXT);
      }
    }
    return function() {
      var index = 0,
          result = length ? funcs[index].apply(this, arguments) : arguments[0];

      while (++index < length) {
        result = funcs[index].call(this, result);
      }
      return result;
    };
  });
}

/**
 * Creates 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.
 *
 * @static
 * @memberOf _
 * @since 3.0.0
 * @category Util
 * @param {...(Function|Function[])} [funcs] Functions to invoke.
 * @returns {Function} Returns the new composite function.
 * @see _.flowRight
 * @example
 *
 * function square(n) {
 *   return n * n;
 * }
 *
 * var addSquare = _.flow(_.add, square);
 * addSquare(1, 2);
 * // => 9
 */
var flow = createFlow();

module.exports = flow;