@alifd/next/lib/util/focus.js

'use strict';

exports.__esModule = true;
exports.getFocusNodeList = getFocusNodeList;
exports.saveLastFocusNode = saveLastFocusNode;
exports.clearLastFocusNode = clearLastFocusNode;
exports.backLastFocusNode = backLastFocusNode;
exports.limitTabRange = limitTabRange;

var _keycode = require('./keycode');

var _keycode2 = _interopRequireDefault(_keycode);

var _object = require('./object');

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

/**
 * 用于切换页面元素的焦点
 */

/**
 * 元素是否可见
 * @private
 * @param   {Element}  node
 * @return  {Boolean}
 */
function _isVisible(node) {
    while (node) {
        var _node = node,
            nodeName = _node.nodeName;

        if (nodeName === 'BODY' || nodeName === 'HTML') {
            break;
        }
        if (node.style.display === 'none' || node.style.visibility === 'hidden') {
            return false;
        }
        node = node.parentNode;
    }
    return true;
}

/**
 * 元素是否可以获取焦点
 * @private
 * @param   {Element}  node
 * @return  {Boolean}
 */
function _isFocusable(node) {
    var nodeName = node.nodeName.toLowerCase();
    var tabIndex = parseInt(node.getAttribute('tabindex'), 10);
    var hasTabIndex = !isNaN(tabIndex) && tabIndex > -1;

    if (_isVisible(node)) {
        if (nodeName === 'input') {
            return !node.disabled && node.type !== 'hidden';
        } else if (['select', 'textarea', 'button'].indexOf(nodeName) > -1) {
            return !node.disabled;
        } else if (nodeName === 'a') {
            return node.getAttribute('href') || hasTabIndex;
        } else {
            return hasTabIndex;
        }
    }
    return false;
}

/**
 * 列出能获取焦点的子节点
 * @param  {Element} node 容器节点
 * @return {Array<Element>}
 */
function getFocusNodeList(node) {
    var res = [];
    var nodeList = node.querySelectorAll('*');

    (0, _object.each)(nodeList, function (item) {
        if (_isFocusable(item)) {
            var method = item.getAttribute('data-auto-focus') ? 'unshift' : 'push';
            res[method](item);
        }
    });

    if (_isFocusable(node)) {
        res.unshift(node);
    }

    return res;
}

// 用于记录上一次获得焦点的无素
var lastFocusElement = null;

/**
 * 保存最近一次获得焦点的无素
 */
function saveLastFocusNode() {
    lastFocusElement = document.activeElement;
}

/**
 * 清除焦点记录
 */
function clearLastFocusNode() {
    lastFocusElement = null;
}

/**
 * 尝试将焦点切换到上一个元素
 */
function backLastFocusNode() {
    if (lastFocusElement) {
        try {
            // 元素可能已经被移动了
            lastFocusElement.focus();
        } catch (e) {
            // ignore ...
        }
    }
}

/**
 * 在限制的范围内切换焦点
 * @param  {Element} node 容器节点
 * @param  {Event} e      键盘事件
 */
function limitTabRange(node, e) {
    if (e.keyCode === _keycode2.default.TAB) {
        var tabNodeList = getFocusNodeList(node);
        var maxIndex = tabNodeList.length - 1;
        var index = tabNodeList.indexOf(document.activeElement);

        if (index > -1) {
            var targetIndex = index + (e.shiftKey ? -1 : 1);
            targetIndex < 0 && (targetIndex = maxIndex);
            targetIndex > maxIndex && (targetIndex = 0);
            tabNodeList[targetIndex].focus();
            e.preventDefault();
        }
    }
}