Equation Ordinal

Numbered equations with \label and \ref for display math in Obsidian.

Write ordinary LaTeX inside $$...$$. The plugin works out the number and renders the tag at display time — nothing is written back to the note, so the file you keep is the source you could paste into a paper.

English | 中文

Why

MathJax renders \tag{...}, but it has no per-note equation counter, and \label / \ref do not behave the way they do in LaTeX. The usual workaround is typing \tag{1}, \tag{2}, … by hand and renumbering everything whenever a formula is inserted in the middle.

Equation Ordinal moves the whole job into the rendering layer:

• the number comes from the order of \label declarations in the file;
• \ref resolves to the same number, already wrapped in parentheses;
• the note on disk is never touched, so your source stays free of injected \tags and you keep full control when you export.

Install

Manual

1. Download manifest.json, main.js and styles.css from this repository.
2. Put them in <vault>/.obsidian/plugins/equation-ordinal/.
3. Reload Obsidian, then enable Equation Ordinal under Settings → Community plugins.

BRAT

Add Junzi-ana/equation-ordinal as a beta plugin.

From source

npm install
npm run build

Usage

Declare a label

$$
\mathrm{d}Y_t = Z_t\,\mathrm{d}W_t - F(t, Y_t, Z_t)\,\mathrm{d}t,\qquad Y_T = \xi
\label{eq:bsde}
$$

\label may sit anywhere inside the display block — at the end, in the middle, or on its own line. It is removed and the tag is placed where MathJax expects it.

Reference it

Combining $\ref{eq:bsde}$ with the estimate above, ...

Works in inline math and in display math. \eqref{...} is accepted as an alias.

The output is already parenthesised — write $\ref{eq:bsde}$, not $(\ref{eq:bsde})$.

Numbering

The counter starts at 1 and increments once per labelled display block.

\label{name}[N] sets the counter to N instead of incrementing it. N is a sequence of numbers and dots; only the segment after the last dot is incremented afterwards.

Rules for N:

• the last segment must be digits: 3, 4.2, 5.1.10 are fine;
• the part before the last dot may contain letters: A.1, A.B.3 are fine;
• trailing dot, leading dot, double dot and a non-numeric last segment are rejected: 1.2., .1, 1..2, 3a.

The counter belongs to the note, not to the file name, so a note that starts with \label{x}[5.1] produces (5.1), (5.2), … in any vault.

Errors

Problems are reported in place and in the console (with file name and line number). Nothing is silently dropped.

An invalid declaration does not consume a number, so one typo never shifts the numbering of everything after it.

Settings

Two commands are available in the command palette: rescan the current file, and print the label table to the console.

How it works

Obsidian renders math with MathJax. The plugin calls loadMathJax(), then wraps MathJax.tex2chtml — the function every formula passes through on its way from TeX to CHTML:

1. Scan. The whole note is scanned synchronously and a label → number table is built. Code blocks, inline code, frontmatter and HTML comments are skipped. Because the table depends only on source order, scrolling, incremental re-rendering and full re-renders can never produce an inconsistent numbering.
2. Rewrite. For each formula, \label{...}[N] is stripped and \tag{number} is appended at a position MathJax accepts — before \end{align} for aligned environments, at the top level for everything else, so cases and aligned inside \left\{ … \right. keep working.
3. Refresh. Each rendered container remembers its original TeX. When an edit changes the numbering table, visible containers are re-rendered in place.

The note file is read-only for this plugin. There is no \tag written into your Markdown, and no separate numbering syntax to learn.

Limitations

• References are resolved within the current note. Cross-file \ref is not supported.
• When several panes show different notes at once, a background pane may be numbered with the foreground note's table. The active pane is always correct.
• Hover previews can show unprocessed math until the note is opened.
• One $$ block may hold at most one \label. Aligned environments share one number.
• A \label inside \text{...} is still recognised, since the scanner works on the TeX string.

Development

npm install
npm test         # unit tests for the counter, scanner and rewriter (node --test)
npm run typecheck
npm run build    # writes main.js next to manifest.json

The pure logic (counter.ts, scanner.ts, rewriter.ts) has no dependency on Obsidian and is tested directly. To develop against a vault, point the build at the plugin folder:

VAULT_PLUGIN_DIR="<vault>/.obsidian/plugins/equation-ordinal" npm run build

License

MIT

中文

给 Obsidian 的行间公式做自动编号，并支持 LaTeX 风格的 \label / \ref 交叉引用。

在 $$...$$ 里写普通的 LaTeX 就行。编号和标签是在渲染时算出来并画上去的，不会写回笔记文件——所以文件里保存的仍然是可以直接粘进论文的那份源码。

为什么需要它

MathJax 能渲染 \tag{...}，但它没有"整篇笔记的公式计数器"，\label / \ref 也不像在 LaTeX 里那样工作。常见的替代做法是手写 \tag{1}、\tag{2}，然后每次在中间插入一个公式，就得把后面全改一遍。

Equation Ordinal 把这件事放到渲染层：

• 编号由 \label 在文件中的出现顺序决定；
• \ref 解析成同一个编号，并自动带上括号；
• 磁盘上的笔记完全不被动过，源码里不会混入插件注入的 \tag，导出时你仍然完全掌握编号。

安装

手动

1. 下载本仓库的 manifest.json、main.js、styles.css；
2. 放进 <vault>/.obsidian/plugins/equation-ordinal/；
3. 重启 Obsidian，在「设置 → 第三方插件」里启用 Equation Ordinal。

BRAT

把 Junzi-ana/equation-ordinal 添加为 beta 插件。

从源码构建

npm install
npm run build

用法

声明标签

$$
\mathrm{d}Y_t = Z_t\,\mathrm{d}W_t - F(t, Y_t, Z_t)\,\mathrm{d}t,\qquad Y_T = \xi
\label{eq:bsde}
$$

\label 可以写在行间公式的任意位置——末尾、中间、单独一行都行。插件会把它删掉，再把 \tag 插到 MathJax 能接受的位置。

引用

结合 $\ref{eq:bsde}$ 与上面的估计可得……

行内公式和行间公式都支持，\eqref{...} 是同义词。

输出本身已带括号，写 $\ref{eq:bsde}$ 即可，不要再套一层 $(\ref{eq:bsde})$。

编号规则

计数器从 1 开始，每遇到一个带 \label 的行间公式就加一。

\label{name}[N] 不递增，而是把计数器直接设为 N。N 由数字和小数点组成，之后只递增最后一个小数点后的那一段。

N 的约束：

• 最后一段必须是数字：3、4.2、5.1.10 都可以；
• 最后一个小数点之前可以含字母：A.1、A.B.3 都可以；
• 末尾带点、开头带点、连续两个点、最后一段非数字，都会被拒绝：1.2.、.1、1..2、3a。

计数器属于笔记本身，与文件名无关。笔记从 \label{x}[5.1] 开始，就会依次得到 (5.1)、(5.2)……

错误码

问题会在公式里就地标出，同时写进控制台（带文件名和行号），不会被静默吞掉。

无效的声明不占用编号，所以一个笔误不会让后面所有公式跟着跳号。

设置

命令面板里有两个命令：重新扫描当前文件、在控制台打印编号表。

工作原理

Obsidian 用 MathJax 渲染数学。插件先 loadMathJax()，然后包住 MathJax.tex2chtml——每个公式从 TeX 变成 CHTML 都要经过这个函数：

1. 扫描：同步扫完整篇笔记，建立 label → 编号 的表。代码块、行内代码、frontmatter、HTML 注释都会被跳过。因为这张表只依赖源码顺序，滚动、增量渲染、整篇重渲都不可能产生前后不一致的编号。
2. 改写：对每个公式，删掉 \label{...}[N]，把 \tag{编号} 插到 MathJax 接受的位置——对齐环境插在 \end{align} 之前，其余情况插在顶层末尾，所以 \left\{ … \right. 里的 cases、aligned 都能正常工作。
3. 刷新：每个渲染出来的容器都记着自己的原始 TeX。当编辑改变了编号表，可见的容器会被原地重渲。

整个过程里笔记文件是只读的：Markdown 里不会多出 \tag，也没有额外的编号语法要学。

已知限制

• 引用只在当前笔记内解析，不支持跨文件 \ref。
• 多个分屏同时显示不同笔记时，后台分屏可能借用前台笔记的编号表；活动分屏始终正确。
• hover 预览可能显示未处理的公式，直到笔记被打开。
• 一个 $$ 块最多一个 \label；对齐环境整体共用一个编号。
• \text{...} 里的 \label 同样会被识别，因为扫描器工作在 TeX 字符串层面。

开发

npm install
npm test         # counter / scanner / rewriter 的单元测试（node --test）
npm run typecheck
npm run build    # 在 manifest.json 旁边生成 main.js

纯逻辑部分（counter.ts、scanner.ts、rewriter.ts）不依赖 Obsidian，可以直接测试。要在 vault 里边改边看，把构建指向插件目录：

VAULT_PLUGIN_DIR="<vault>/.obsidian/plugins/equation-ordinal" npm run build

许可

MIT