Can I add custom attribute to HTML tag?

Question

Can I add custom attribute to HTML tag like this: <tag myAttri="myVal" />

Answer 1

Here is the example:

document.getElementsByTagName("html").foo="bar"

Here is another example how to set custom attributes into body tag element:

document.getElementsByTagName('body')[0].dataset.attr1 = "foo";
document.getElementsByTagName('body')[0].dataset.attr2 = "bar";

Then read the attribute by:

attr1 = document.getElementsByTagName('body')[0].dataset.attr1
attr2 = document.getElementsByTagName('body')[0].dataset.attr2

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You can test above code in Console in DevTools, e.g.