I've been a professional C, Perl, PHP and Python developer.
I'm an ex-sysadmin from the late 20th century.
These days I do more Javascript and CSS and whatnot, and promote UX and accessibility.
If you use const reHash = /(?:\s|^)?#[A-Za-z0-9\-\.\_]+(?:\s|$)/g then you'll match " #hello" as " #hello", with the space at the start. I see you're using trim() to fix this later in the code.
You could use this instead, which should cover all the bases using \B to match against non-word-boundary characters at the start and \b to match word-boundaries at the end: /\B#[A-Za-z0-9\-\.\_]+\b/g
This means you don't need to do the \s|^ trickery.
"#one two#three #four five #six_seven".match(/\B#[A-Za-z0-9\-\.\_]+\b/g)//Â ["#one", "#four", "six_seven"]
EDIT: come to think of it, you don't need to escape the characters inside [] either, even the - if it's the last character. And you can make it case-insensitive with the /i flag.
/\B#[a-z0-9._-]+\b/gi
Final answer.
Wait, no you can improve that by making sure it starts with a letter.
Thanks for the finer points. So in [] or a character class|set the only characters that must be escaped are \ (backslash), ^ and -. And hyphen can be un-escaped if its last. I have to research more on word boundaries. I sort of hacked my hashtag solution because the preceding match would gobble up the space character need with the next. Wow, trying to explain RegEx thought is ridiculous. But yah, it is crazy that one line of code can take this long to understand.
I've been a professional C, Perl, PHP and Python developer.
I'm an ex-sysadmin from the late 20th century.
These days I do more Javascript and CSS and whatnot, and promote UX and accessibility.
If you use
const reHash = /(?:\s|^)?#[A-Za-z0-9\-\.\_]+(?:\s|$)/gthen you'll match " #hello" as " #hello", with the space at the start. I see you're usingtrim()to fix this later in the code.You could use this instead, which should cover all the bases using
\Bto match against non-word-boundary characters at the start and\bto match word-boundaries at the end:/\B#[A-Za-z0-9\-\.\_]+\b/gThis means you don't need to do the
\s|^trickery.EDIT: come to think of it, you don't need to escape the characters inside
[]either, even the-if it's the last character. And you can make it case-insensitive with the/iflag./\B#[a-z0-9._-]+\b/giFinal answer.
Wait, no you can improve that by making sure it starts with a letter.
/\B#[a-z][a-z0-9._-]*\b/giFinal final answer :)
Thanks for the finer points. So in
[]or acharacter class|setthe only characters that must be escaped are\(backslash),^and-. And hyphen can be un-escaped if its last. I have to research more on word boundaries. I sort of hacked my hashtag solution because the preceding match would gobble up the space character need with the next. Wow, trying to explain RegEx thought is ridiculous. But yah, it is crazy that one line of code can take this long to understand.You don't need to escape
^in a character class because it has no ambiguous meaning. Same with$.