查看“︁MediaWiki:Gadget-SelectionCounter.js”︁的源代码

/* ================================================================
   MediaWiki Gadget: SelectionCounter
   功能：
   - 选中文本时显示字数统计
   - 与 RightToolbar 风格一致
   ================================================================= */

mw.loader.using(['mediawiki.util']).then(function () {
    if (window.SelectionCounterLoaded) {
        return;
    }
    window.SelectionCounterLoaded = true;

    $(function () {
        var $counter = $('#mw-selection-counter');

        if (!$counter.length) {
            $counter = $('<div id="mw-selection-counter" class="mw-selection-counter" role="status" aria-live="polite"></div>')
                .hide()
                .appendTo('body');
        }

        var rafId = null;
        var pollTimer = null;
        var lastText = null;

        function getSelectionText() {
            var selection = window.getSelection();
            if (!selection || selection.isCollapsed) {
                return '';
            }
            return String(selection).trim();
        }

        function updateCounter() {
            rafId = null;
            var active = document.activeElement;
            if (active && (active.tagName === 'INPUT' || active.tagName === 'TEXTAREA' || active.isContentEditable)) {
                if (lastText !== null) {
                    lastText = null;
                    $counter.hide();
                }
                return;
            }

            var text = getSelectionText();
            if (!text) {
                if (lastText !== null) {
                    lastText = null;
                    $counter.hide();
                }
                return;
            }

            if (text === lastText) {
                return;
            }

            lastText = text;
            var count = Array.from(text).length;
            $counter.text('已选 ' + count + ' 字').show();
        }

        function scheduleUpdate() {
            if (rafId) {
                return;
            }
            rafId = window.requestAnimationFrame(updateCounter);
        }

        function startPolling() {
            if (pollTimer) {
                return;
            }
            pollTimer = window.setInterval(updateCounter, 500);
        }

        function stopPolling() {
            if (!pollTimer) {
                return;
            }
            window.clearInterval(pollTimer);
            pollTimer = null;
        }

        document.addEventListener('selectionchange', scheduleUpdate);
        document.addEventListener('mouseup', scheduleUpdate);
        document.addEventListener('keyup', scheduleUpdate);
        document.addEventListener('touchend', scheduleUpdate, { passive: true });
        window.addEventListener('focus', startPolling);
        window.addEventListener('blur', stopPolling);
        document.addEventListener('visibilitychange', function () {
            if (document.hidden) {
                stopPolling();
                return;
            }
            startPolling();
        });

        startPolling();
    });
});