var closest = require('./closest');
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/**
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* Delegates event to a selector.
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*
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* @param {Element} element
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* @param {String} selector
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* @param {String} type
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* @param {Function} callback
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* @param {Boolean} useCapture
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* @return {Object}
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*/
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function _delegate(element, selector, type, callback, useCapture) {
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var listenerFn = listener.apply(this, arguments);
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element.addEventListener(type, listenerFn, useCapture);
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return {
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destroy: function() {
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element.removeEventListener(type, listenerFn, useCapture);
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}
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}
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}
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/**
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* Delegates event to a selector.
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*
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* @param {Element|String|Array} [elements]
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* @param {String} selector
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* @param {String} type
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* @param {Function} callback
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* @param {Boolean} useCapture
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* @return {Object}
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*/
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function delegate(elements, selector, type, callback, useCapture) {
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// Handle the regular Element usage
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if (typeof elements.addEventListener === 'function') {
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return _delegate.apply(null, arguments);
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}
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// Handle Element-less usage, it defaults to global delegation
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if (typeof type === 'function') {
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// Use `document` as the first parameter, then apply arguments
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// This is a short way to .unshift `arguments` without running into deoptimizations
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return _delegate.bind(null, document).apply(null, arguments);
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}
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// Handle Selector-based usage
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if (typeof elements === 'string') {
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elements = document.querySelectorAll(elements);
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}
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// Handle Array-like based usage
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return Array.prototype.map.call(elements, function (element) {
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return _delegate(element, selector, type, callback, useCapture);
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});
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}
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/**
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* Finds closest match and invokes callback.
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*
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* @param {Element} element
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* @param {String} selector
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* @param {String} type
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* @param {Function} callback
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* @return {Function}
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*/
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function listener(element, selector, type, callback) {
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return function(e) {
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e.delegateTarget = closest(e.target, selector);
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if (e.delegateTarget) {
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callback.call(element, e);
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}
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}
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}
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module.exports = delegate;
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