diff --git a/packages/mermaid/src/assignWithDepth.js b/packages/mermaid/src/assignWithDepth.ts
similarity index 65%
rename from packages/mermaid/src/assignWithDepth.js
rename to packages/mermaid/src/assignWithDepth.ts
index 6f2e706abe..831825779d 100644
--- a/packages/mermaid/src/assignWithDepth.js
+++ b/packages/mermaid/src/assignWithDepth.ts
@@ -1,32 +1,36 @@
-'use strict';
+/* eslint-disable @typescript-eslint/no-explicit-any */
+
 /**
- * @function assignWithDepth Extends the functionality of {@link ObjectConstructor.assign} with the
+ * assignWithDepth Extends the functionality of {@link ObjectConstructor.assign} with the
  *   ability to merge arbitrary-depth objects For each key in src with path `k` (recursively)
  *   performs an Object.assign(dst[`k`], src[`k`]) with a slight change from the typical handling of
- *   undefined for dst[`k`]: instead of raising an error, dst[`k`] is auto-initialized to {} and
+ *   undefined for dst[`k`]: instead of raising an error, dst[`k`] is auto-initialized to `{}` and
  *   effectively merged with src[`k`]<p> Additionally, dissimilar types will not clobber unless the
  *   config.clobber parameter === true. Example:
  *
- *   ```js
- *   let config_0 = { foo: { bar: 'bar' }, bar: 'foo' };
- *   let config_1 = { foo: 'foo', bar: 'bar' };
- *   let result = assignWithDepth(config_0, config_1);
- *   console.log(result);
- *   //-> result: { foo: { bar: 'bar' }, bar: 'bar' }
- *   ```
+ * ```
+ * const config_0 = { foo: { bar: 'bar' }, bar: 'foo' };
+ * const config_1 = { foo: 'foo', bar: 'bar' };
+ * const result = assignWithDepth(config_0, config_1);
+ * console.log(result);
+ * //-> result: { foo: { bar: 'bar' }, bar: 'bar' }
+ * ```
  *
  *   Traditional Object.assign would have clobbered foo in config_0 with foo in config_1. If src is a
  *   destructured array of objects and dst is not an array, assignWithDepth will apply each element
  *   of src to dst in order.
- * @param {any} dst - The destination of the merge
- * @param {any} src - The source object(s) to merge into destination
- * @param {{ depth: number; clobber: boolean }} [config] - Depth: depth
- *   to traverse within src and dst for merging - clobber: should dissimilar types clobber (default:
- *   { depth: 2, clobber: false }). Default is `{ depth: 2, clobber: false }`
- * @returns {any}
+ * @param dst - The destination of the merge
+ * @param src - The source object(s) to merge into destination
+ * @param config -
+ * * depth: depth to traverse within src and dst for merging
+ * * clobber: should dissimilar types clobber
  */
-const assignWithDepth = function (dst, src, config) {
-  const { depth, clobber } = Object.assign({ depth: 2, clobber: false }, config);
+const assignWithDepth = (
+  dst: any,
+  src: any,
+  { depth = 2, clobber = false }: { depth?: number; clobber?: boolean } = {}
+): any => {
+  const config: { depth: number; clobber: boolean } = { depth, clobber };
   if (Array.isArray(src) && !Array.isArray(dst)) {
     src.forEach((s) => assignWithDepth(dst, s, config));
     return dst;