javascript - 延迟 javascript - 什么是正确的 html 语法 defer 或 defer ="defer"

Question

在 javascript 中使用 defer 属性的正确语法是什么？

我见过有两种方式:

1:

<script defer  >...</script>

2:

<script defer="defer">...</script>

根据经验 [和我找不到的引用资料]，我更倾向于使用第二个选项，但我只是仔细检查了 official w3c site看来选项 1 是正确的。

谢谢

Answer 1

defer 是一个 boolean attribute ^{[HTML 4.01 spec]} :

Some attributes play the role of boolean variables (e.g., the selected attribute for the OPTION element). Their appearance in the start tag of an element implies that the value of the attribute is "true". Their absence implies a value of "false".

[...]

In HTML, boolean attributes may appear in minimized form -- the attribute's value appears alone in the element's start tag. Thus, selected may be set by writing:

<OPTION selected>

instead of:

<OPTION selected="selected">

Authors should be aware that many user agents only recognize the minimized form of boolean attributes and not the full form.

但是，如果您使用 XHTML，则必须使用第二种形式，因为 XHTML 遵循 XML 语法，其中属性始终必须具有值。