fix: js string split (#38233)

fix #38229

web_src/js/utils/string.test.ts

@@ -0,0 +1,13 @@
+import {cutString} from './string.ts';
+
+test('cutString', () => {
+  let [before, after, ok] = cutString('a = b = c', '=');
+  expect(before).toBe('a ');
+  expect(after).toBe(' b = c');
+  expect(ok).toBe(true);
+
+  [before, after, ok] = cutString(' a ', '=');
+  expect(before).toBe(' a ');
+  expect(after).toBe('');
+  expect(ok).toBe(false);
+});