From 09633dda580a92e8779d5a9abeab9792ffdc2477 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E8=A1=97=E8=A7=92=E5=B0=8F=E6=9E=97?= <1013335014@qq.com>
Date: Wed, 5 Jun 2024 15:46:16 +0800
Subject: [PATCH] =?UTF-8?q?Feat=EF=BC=9A=E9=99=8D=E7=BA=A7Formula=E6=8F=92?=
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---
 simple-mind-map/src/plugins/Formula.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/simple-mind-map/src/plugins/Formula.js b/simple-mind-map/src/plugins/Formula.js
index 5d628de3..19001625 100644
--- a/simple-mind-map/src/plugins/Formula.js
+++ b/simple-mind-map/src/plugins/Formula.js
@@ -101,7 +101,7 @@ class Formula {
           const m = [...insert.matchAll(/\$.+?\$/g)]
           const arr = insert.split(/\$.+?\$/g)
           for (let j = m.length - 1; j >= 0; j--) {
-            const exp = m[j]?.[0].slice(1, -1) ?? null // $...$ 之间的表达式
+            const exp = m[j] && m[j][0] ? m[j][0].slice(1, -1) || null : null // $...$ 之间的表达式
             if (exp !== null && exp.trim().length > 0) {
               const isLegal = this.checkFormulaIsLegal(exp)
               if (isLegal) {