Determining the Default Submit Button in HTML Forms

When a form is submitted without an explicit submit button, such as by pressing Enter or using JavaScript, browsers typically follow specific conventions to identify the default submit button. However, this behavior can vary depending on the browser.

Submitting by Enter

According to the HTML specifications, entering in a non-textarea field within a form should not trigger form submission. However, browsers have implemented their own behavior:

• Firefox, Opera, Safari: Use the first submit button in the form.
• Internet Explorer: May use the first submit button or none, depending on the context.

Submitting via JavaScript

When submitting a form programmatically using formElement.submit(), no submit button is considered successful, and their values are not included in the submitted data. If the submit button's click() method is used, that specific button is considered active.

Browser Differences

The specifications do not define a standard for submit button determination when Enter is pressed. Browsers may use heuristics such as:

• Internet Explorer: First submit button in the source order.
• Firefox, Opera: Submit button with the lowest tabindex, falling back to the first defined if none specified.
• Other Browsers: Behavior is browser-specific and may depend on factors like non-default value attributes.

Conclusion

The default submit button behavior when submitting via Enter or JavaScript is not standardized and varies among browsers. To ensure consistent behavior, it is recommended to avoid relying on specific behaviors and instead use explicit submit buttons whenever possible.