有時在HTML頁面form的input里按了回車鍵會提交該表單,并且form的submit按鈕的click事件也會被觸發.這是什么原理呢?是因為form的隱式提交(Implicit submission)機制

在https://www.w3.org/TR/html52/sec-forms.html#implicit-submission中是這么解釋的

A form element’s default button is the first Submit Button in tree order whose form owner is that form element.

form的第一個submit按鈕作為default button

If the user agent supports letting the user submit a form implicitly (for example, on some platforms hitting the "enter" key while a text field is focused implicitly submits the form), then doing so for a form whose default button has a defined activation behavior must cause the user agent to run synthetic click activation steps on that default button.

瀏覽器隱式提交時要觸發default button的click事件.在某些平臺上,text field獲得焦點時,按回車鍵會觸發隱式提交

If the form has no Submit Button, then the implicit submission mechanism must do nothing if the form has more than one field that blocks implicit submission, and must submit the form element from the form element itself otherwise.

For the purpose of the previous paragraph, an element is a field that blocks implicit submission of a form element if it is an input element whose form owner is that form element and whose type attribute is in one of the following states: Text, Search, URL, Telephone, E-mail, Password, Local Date and Time, Date, Month, Week, Time, Number

form里有超過一個的input時,必須阻止隱式提交

在早期的HTML規范中,還有如下描述

When there is only one single-line text input field in a form, the user agent should accept Enter in that field as a request to submit the form.

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