chromium/src/third_party/blink/perf_tests/speedometer/resources/todomvc/vanilla-examples/vanillajs/js/helpers.js

/*global NodeList */
(function (window) {
    'use strict';

    // Get element(s) by CSS selector:
    window.qs = function (selector, scope) {
        return (scope || document).querySelector(selector);
    };
    window.qsa = function (selector, scope) {
        return (scope || document).querySelectorAll(selector);
    };

    // addEventListener wrapper:
    window.$on = function (target, type, callback, useCapture) {
        target.addEventListener(type, callback, !!useCapture);
    };

    // Attach a handler to event for all elements that match the selector,
    // now or in the future, based on a root element
    window.$delegate = function (target, selector, type, handler) {
        function dispatchEvent(event) {
            var targetElement = event.target;
            var potentialElements = window.qsa(selector, target);
            var hasMatch = Array.prototype.indexOf.call(potentialElements, targetElement) >= 0;

            if (hasMatch) {
                handler.call(targetElement, event);
            }
        }

        // https://developer.mozilla.org/en-US/docs/Web/Events/blur
        var useCapture = type === 'blur' || type === 'focus';

        window.$on(target, type, dispatchEvent, useCapture);
    };

    // Find the element's parent with the given tag name:
    // $parent(qs('a'), 'div');
    window.$parent = function (element, tagName) {
        if (!element.parentNode) {
            return;
        }
        if (element.parentNode.tagName.toLowerCase() === tagName.toLowerCase()) {
            return element.parentNode;
        }
        return window.$parent(element.parentNode, tagName);
    };

    // Allow for looping on nodes by chaining:
    // qsa('.foo').forEach(function () {})
    NodeList.prototype.forEach = Array.prototype.forEach;
})(window);