codex-team/editor.js · error · Error

Index should be a number

Error message

Index should be a number

What it means

blocks.insertMany(blocks, index) validates the insertion index via validateIndex, which requires it to be a number. Passing a string, undefined, null, or NaN triggers this error before any insertion happens.

Source

Thrown at src/components/modules/api/blocks.ts:417

        data,
      });
    });

    this.Editor.BlockManager.insertMany(blocksToInsert, index);

    // we cast to any because our BlockAPI has no "new" signature
    // eslint-disable-next-line @typescript-eslint/no-explicit-any
    return blocksToInsert.map((block) => new (BlockAPI as any)(block));
  };

  /**
   * Validated block index and throws an error if it's invalid
   *
   * @param index - index to validate
   */
  private validateIndex(index: unknown): void {
    if (typeof index !== 'number') {
      throw new Error('Index should be a number');
    }

    if (index < 0) {
      throw new Error(`Index should be greater than or equal to 0`);
    }

    if (index === null) {
      throw new Error(`Index should be greater than or equal to 0`);
    }
  }
}

View on GitHub (pinned to 5f45dabbe5)

Solutions

1. Coerce/Number()-validate the index before calling insertMany
2. Pass a literal number or omit-dependent default computed as number
3. Add a type guard isNumber(index) in the calling code

Example fix

// before
editor.blocks.insertMany(blocks, blockEl.dataset.index);
// after
editor.blocks.insertMany(blocks, Number(blockEl.dataset.index));

if (typeof index !== 'number' || Number.isNaN(index)) index = editor.blocks.getBlocksAmount(); editor.blocks.insertMany(blocks, index);

const isNumberIndex = (i: unknown): i is number => typeof i === 'number' && !Number.isNaN(i);

try { editor.blocks.insertMany(blocks, index); } catch (e) { if (e instanceof Error && e.message === 'Index should be a number') { editor.blocks.insertMany(blocks, Number(index)); return; } throw e; }

When it happens

Trigger: Calling editor.blocks.insertMany(blocks, '2'), passing undefined for the index argument, or sourcing the index from DOM dataset/URL params as a string.

Common situations: Index read from data attributes or query strings (always strings); optional-index code paths that forward undefined; refactors that changed the parameter type.

Understand the failure class

Background: Invalid argument type errors: "must be of type string", "expected X, got Y", and ERR_INVALID_ARG_TYPE explained — this error's family across 15 libraries.

Related errors

• Index should be greater than or equal to 0
• Unable to move Block down since it is already the last
• Unable to move Block up since it is already the first
• Incorrect data passed to the render() method
• Block with id "${id}" not found

AI-assisted analysis of codex-team/editor.js@5f45dabbe5 (2026-08-27). Data as JSON: /api/errors/149bcea66712d155. Report an issue: GitHub.