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