#2733 Add error if level exceeds 9

src/file/numbering/level.spec.ts

@@ -0,0 +1,25 @@
+import { expect } from "chai";
+
+import { LevelFormat, LevelSuffix } from ".";
+import { AlignmentType } from "..";
+
+import { Level } from "./level";
+
+describe("Level", () => {
+    describe("#constructor", () => {
+        it("should throw an error if level exceeds 9", () => {
+            expect(
+                () =>
+                    new Level({
+                        level: 10,
+                        format: LevelFormat.BULLET,
+                        text: "test",
+                        alignment: AlignmentType.BOTH,
+                        start: 3,
+                        style: { run: {}, paragraph: {} },
+                        suffix: LevelSuffix.SPACE,
+                    }),
+            ).to.throw();
+        });
+    });
+});

src/file/numbering/level.ts

@@ -161,6 +161,12 @@ export class LevelBase extends XmlComponent {
         this.root.push(this.paragraphProperties);
         this.root.push(this.runProperties);
 
+        if (level > 9) {
+            throw new Error(
+                "Level cannot be greater than 9. Read more here: https://answers.microsoft.com/en-us/msoffice/forum/all/does-word-support-more-than-9-list-levels/d130fdcd-1781-446d-8c84-c6c79124e4d7",
+            );
+        }
+
         this.root.push(
             new LevelAttributes({
                 ilvl: decimalNumber(level),