cond.js (1613B)
1 var apply = require('./_apply'), 2 arrayMap = require('./_arrayMap'), 3 baseIteratee = require('./_baseIteratee'), 4 baseRest = require('./_baseRest'); 5 6 /** Error message constants. */ 7 var FUNC_ERROR_TEXT = 'Expected a function'; 8 9 /** 10 * Creates a function that iterates over `pairs` and invokes the corresponding 11 * function of the first predicate to return truthy. The predicate-function 12 * pairs are invoked with the `this` binding and arguments of the created 13 * function. 14 * 15 * @static 16 * @memberOf _ 17 * @since 4.0.0 18 * @category Util 19 * @param {Array} pairs The predicate-function pairs. 20 * @returns {Function} Returns the new composite function. 21 * @example 22 * 23 * var func = _.cond([ 24 * [_.matches({ 'a': 1 }), _.constant('matches A')], 25 * [_.conforms({ 'b': _.isNumber }), _.constant('matches B')], 26 * [_.stubTrue, _.constant('no match')] 27 * ]); 28 * 29 * func({ 'a': 1, 'b': 2 }); 30 * // => 'matches A' 31 * 32 * func({ 'a': 0, 'b': 1 }); 33 * // => 'matches B' 34 * 35 * func({ 'a': '1', 'b': '2' }); 36 * // => 'no match' 37 */ 38 function cond(pairs) { 39 var length = pairs == null ? 0 : pairs.length, 40 toIteratee = baseIteratee; 41 42 pairs = !length ? [] : arrayMap(pairs, function(pair) { 43 if (typeof pair[1] != 'function') { 44 throw new TypeError(FUNC_ERROR_TEXT); 45 } 46 return [toIteratee(pair[0]), pair[1]]; 47 }); 48 49 return baseRest(function(args) { 50 var index = -1; 51 while (++index < length) { 52 var pair = pairs[index]; 53 if (apply(pair[0], this, args)) { 54 return apply(pair[1], this, args); 55 } 56 } 57 }); 58 } 59 60 module.exports = cond;