chromium/src/third_party/blink/perf_tests/speedometer/resources/todomvc/vanilla-examples/es2015/src/helpers.js

'use strict';


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

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

function qsa(selector, scope) {
    return (scope || document).querySelectorAll(selector);
}

// addEventListener wrapper:
function $on(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
function $delegate(target, selector, type, handler) {
    let dispatchEvent = event => {
        const targetElement = event.target;
        const potentialElements = qsa(selector, target);
        const hasMatch = Array.prototype.indexOf.call(potentialElements, targetElement) >= 0;

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

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

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

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

    if (element.parentNode.tagName.toLowerCase() === tagName.toLowerCase()) {
        return element.parentNode;
    }

    return $parent(element.parentNode, tagName);
}