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61 lines
1.6 KiB
JavaScript
61 lines
1.6 KiB
JavaScript
6 years ago
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var apply = require('./_apply'),
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arrayMap = require('./_arrayMap'),
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baseIteratee = require('./_baseIteratee'),
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baseRest = require('./_baseRest');
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/** Error message constants. */
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var FUNC_ERROR_TEXT = 'Expected a function';
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/**
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* Creates a function that iterates over `pairs` and invokes the corresponding
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* function of the first predicate to return truthy. The predicate-function
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* pairs are invoked with the `this` binding and arguments of the created
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* function.
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*
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* @static
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* @memberOf _
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* @since 4.0.0
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* @category Util
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* @param {Array} pairs The predicate-function pairs.
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* @returns {Function} Returns the new composite function.
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* @example
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*
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* var func = _.cond([
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* [_.matches({ 'a': 1 }), _.constant('matches A')],
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* [_.conforms({ 'b': _.isNumber }), _.constant('matches B')],
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* [_.stubTrue, _.constant('no match')]
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* ]);
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*
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* func({ 'a': 1, 'b': 2 });
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* // => 'matches A'
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*
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* func({ 'a': 0, 'b': 1 });
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* // => 'matches B'
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*
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* func({ 'a': '1', 'b': '2' });
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* // => 'no match'
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*/
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function cond(pairs) {
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var length = pairs == null ? 0 : pairs.length,
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toIteratee = baseIteratee;
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pairs = !length ? [] : arrayMap(pairs, function(pair) {
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if (typeof pair[1] != 'function') {
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throw new TypeError(FUNC_ERROR_TEXT);
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}
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return [toIteratee(pair[0]), pair[1]];
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});
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return baseRest(function(args) {
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var index = -1;
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while (++index < length) {
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var pair = pairs[index];
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if (apply(pair[0], this, args)) {
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return apply(pair[1], this, args);
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}
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}
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});
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}
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module.exports = cond;
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