The only exception here are boolean type attributes. A Boolean attribute indicates that the element is not yet, or is no longer, relevant. The browser won't render such elements. 3.2.2 Boolean attributes. You can use the Boolean() function to find out if an expression (or a variable) is true: Boolean attributes in HTML are the one which do not have any value. Boolean attributes in HTML are normally used to indicate things like whether a checkbox is checked or whether an option is selected or whether an input is disabled. There are occasions where we need to add or omit an empty attribute. Because all attributes must be strings, the value we’re binding to the attribute must be able to convert to a string. Instead, HTML implements something called short-form evaluation, which means that it is the presence of the boolean attribute in a HTML tag that determines whether it is true or false. When present, it specifies that an element is not yet, or is no longer, relevant. This means that codes like does not make sense in correct HTML. It is a Boolean attribute and also new in HTML5. Set up an observed (not reflected) attribute with the lowercased name of each property. This allows the input to accept a comma-separated list of email addresses. We can use this attribute in two tags