Question

unfortunately i’m poor in regex! can you guide me to write a regex in javascript which can determine my terms input box. a user should input terms with this format:

#(all alphanumeric chars + blank + dash + quotation )

for example:

#keyword1#key word2#keyword3#key-word4#key'word5

and these inputs should be illegal:

#####
##keyword1#key2#
# #keyword
#!%^&

Answer 1

/#[a-zA-Z0-9][a-zA-Z0-9 '-]+/

When you said “# #keyword” should be invalid, I’ve assumed you mean “# ” should be invalid and “#keyword” should be extracted from that string. The first ‘box’ means a keyword will always begin with a lowercase letter, uppercase letter, or number. If thats too restrictive and you want to allow for example “#-keyword”, just add dash in before the first close-square-bracket, like so:

/#[a-zA-Z0-9-][a-zA-Z0-9 '-]+/

And to return an array of results in javascript, apply it to the string using the “global” modifier (‘g’ after the second slash):

arrayOfKeywords = keywordString.match(/#[a-zA-Z0-9-][a-zA-Z0-9 '-]+/g);

You may wish to see this code at my test page. Regular-expressions.info is a useful site to learn more about regular expressions. They also have an interactive page to test regexes on, which can be useful when playing around.