[js] 用代码片段让思源笔记发布到微信公众号支持公式渲染

更完整的代码片段见：[js] 思源笔记粘贴到微信公众号处理公式、链接、多级列表 - 链滴

最近沉迷统计学，打算在微信公众号发统计分析的笔记，但是思源笔记不支持粘贴公式到微信公众号，行内公式和块级公式都不行，非常苦恼

之前提了这个 issue，发布到微信公众号支持公式渲染 · Issue #12571 · siyuan-note/siyuan，等 DV 两口子解决也是遥遥无期

只好自己尝试解决了，因为正好知道微信 Markdown 编辑器 | Doocs 开源社区这个编辑器是支持 markdown 公式粘贴到微信公众号，于是扒代码，把代码发给 GPT 如何改进思源笔记的预览模式……花了一小时

竟然真的给我问出来了哈哈哈

代码片段

(async () => {
    // 定义观察DOM变化的函数
    function observeDomChange(targetNode, callback) {
        const config = { childList: true, subtree: true };
        const observer = new MutationObserver((mutationsList) => {
            for (const mutation of mutationsList) {
                if (mutation.type === 'childList') {
                    callback(mutation);
                }
            }
        });
        observer.observe(targetNode, config);
        return observer;
    }

    const targetNode = document.body;

    // 开始观察DOM变化，并在检测到.color__square元素时运行updateColors
    observeDomChange(targetNode, async (mutation) => {
        const hasMathBlock = mutation.target.querySelector('.layout__wnd--active .protyle:not(.fn__none) .protyle-preview>.b3-typography div[data-subtype="math"]:not([data-repleaced="true"])');
        const hasInlineMath = mutation.target.querySelector('.layout__wnd--active .protyle:not(.fn__none) .protyle-preview>.b3-typography span[data-type="inline-math"]:not([data-repleaced="true"])');
        if (mutation.target.classList.contains("protyle-preview")) {
            if (hasMathBlock || hasInlineMath) {
                await fetchSyncPost('/api/notification/pushMsg', {
                    "msg": "正在处理公式",
                    "timeout": 5000
                });
                loadMathJax(async () => {
                    await Promise.all([renderMathBlocks(), renderInlineMath()]);
                    console.log('MathJax has been loaded!');
                    await fetchSyncPost('/api/notification/pushMsg', {
                        "msg": "公式处理完毕",
                        "timeout": 5000
                    });
                });
            }
        }
    });

    function createRenderer(display) {
        return (mathContent) => {
            const cleanedContent = mathContent.replace(/\\displaystyle\s*{([^}]*)}/g, '$1');

            window.MathJax.texReset();
            const mjxContainer = window.MathJax.tex2svg(cleanedContent, { display });
            const svg = mjxContainer.firstChild;
            const width = svg.style[`min-width`] || svg.getAttribute(`width`);
            svg.removeAttribute(`width`);
            svg.style = `max-width: 70vw !important;`;
            svg.style.width = width;
            svg.style.display = `initial`;
            if (display) {
                return `<section style="box-sizing: border-box; border-width: 0px; border-style: solid; border-color: hsl(var(--border)); user-select: text !important; color: rgb(10, 10, 10); font-family: ui-sans-serif, system-ui, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji"; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; white-space: normal; background-color: rgb(255, 255, 255); text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial; text-align: center; overflow: auto;">${svg.outerHTML}</section>`;
            }
            return svg.outerHTML;
        };
    }

    async function renderMathBlocks() {
        const mathBlocks = document.querySelectorAll('.b3-typography div[data-subtype="math"]:not([data-repleaced="true"])');
        const renderBlock = createRenderer(true);

        return Promise.all(Array.from(mathBlocks).map(async (block) => {
            const mathContent = block.getAttribute('data-content');
            try {
                block.innerHTML = renderBlock(mathContent);
                block.setAttribute('data-repleaced', 'true');
            } catch (error) {
                console.error('Error rendering MathJax block:', error);
            }
        }));
    }

    async function renderInlineMath() {
        const inlineMaths = document.querySelectorAll('span[data-type="inline-math"]:not([data-repleaced="true"])');
        const renderInline = createRenderer(false);

        return Promise.all(Array.from(inlineMaths).map(async (span) => {
            const mathContent = span.getAttribute('data-content');
            try {
                span.innerHTML = renderInline(mathContent);
                span.style.verticalAlign = 'middle';
                span.style.lineHeight = '1';
                span.setAttribute('data-repleaced', 'true');
            } catch (error) {
                console.error('Error rendering MathJax inline:', error);
            }
        }));
    }

    function loadMathJax(callback) {
        window.MathJax = {
            tex: {
                inlineMath: [['$', '$'], ['\\(', '\\)']]
            },
            svg: {
                fontCache: 'none'
            }
        };

        const script = document.createElement('script');
        script.src = 'https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-svg.js';
        script.async = true;
        script.onload = callback;
        document.head.appendChild(script);
    }

    async function fetchSyncPost(url, data, returnType = 'json') {
        const init = {
            method: "POST",
            headers: {
                'Content-Type': 'application/json'
            },
            body: JSON.stringify(data)
        };
        try {
            const res = await fetch(url, init);
            return returnType === 'json' ? await res.json() : await res.text();
        } catch (e) {
            console.log(e);
            return returnType === 'json' ? { code: e.code || 1, msg: e.message || "", data: null } : "";
        }
    }
})();

预览

没处理前：块公式惨不忍睹，行内公式有些看着正常，但是手机一预览一旦有下标、上标就会跑到其他地方去

代码片段运行后：行内公式和公式块都以 svg 格式插入公式，一切正常