node_modules/delegate/src/delegate.js

var closest = require('./closest');

/**
 * Delegates event to a selector.
 *
 * @param {Element} element
 * @param {String} selector
 * @param {String} type
 * @param {Function} callback
 * @param {Boolean} useCapture
 * @return {Object}
 */
function delegate(element, selector, type, callback, useCapture) {
    var listenerFn = listener.apply(this, arguments);

    element.addEventListener(type, listenerFn, useCapture);

    return {
        destroy: function() {
            element.removeEventListener(type, listenerFn, useCapture);
        }
    }
}

/**
 * Finds closest match and invokes callback.
 *
 * @param {Element} element
 * @param {String} selector
 * @param {String} type
 * @param {Function} callback
 * @return {Function}
 */
function listener(element, selector, type, callback) {
    return function(e) {
        e.delegateTarget = closest(e.target, selector);

        if (e.delegateTarget) {
            callback.call(element, e);
        }
    }
}

module.exports = delegate;