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What does it mean to have leading or trailing spaces?
Trailing space is all whitespace located at the end of a line, without any other characters following it. This includes spaces (what you called a blank) as well as tabs \t , carriage returns \r , etc. There are 25 unicode characters that are considered whitespace, which are listed on Wikipedia.
Why are spaces allowed in usernames?
Usernames typically don’t contain spaces, so allowing users to type in an invalid input and silently removing the space is overly presumptuous for the UX. It’s better to detect the interstitial space and inform the user (e.g. Usernames can’t contain spaces ) so they can check the username again.
What are leading and trailing zeros?
Zeros attached to the beginning of a number in this way are called leading zeros. In decimals, this idea of zeros that don’t add value to a number can be extended to trailing zeros. A trailing zero is any zero that appears to the right of both the decimal point and every digit other than zero.
When to use leading and trailing spaces in attribute values?
The leading and trailing spaces are more or less meaningless. Similar to the examples above using IDs, an exception would be if you were using the attribute selector to access the class attribute, as shown in the following example code and demo:
Is it OK to use trailing space in HTML attribute?
In most cases, you should not use a leading or trailing space in an HTML attribute value. For example, if you add a leading or trailing space to an ID attribute, you wouldn’t be able to hook into that value in CSS using the ID selector (not that you use IDs as selectors, right?):
Can a leading space be used in an HTML attribute?
In most cases, you should not use a leading or trailing space in an HTML attribute value. For example, if you add a leading or trailing space to an ID attribute, you wouldn’t be able to hook into that value in CSS using the ID selector (not that you use IDs as selectors, right?): This happens because spaces are not allowed in an ID selector.
Is the leading space in the id attribute meaningful?
As is the case with the ID attribute, the leading space in each of these type attributes is meaningful. So the above elements will not display as number, range, and button types, as specified, but rather as text inputs, which is the default for when the type attribute is missing.