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);
+});

web_src/js/utils/string.ts

@@ -0,0 +1,5 @@
+export function cutString(s: string, sep: string): [string, string, boolean] {
+  const index = s.indexOf(sep);
+  if (index === -1) return [s, '', false];
+  return [s.substring(0, index), s.substring(index + sep.length), true];
+}