JavaScript regex replace as alphanumeric with spaces only between character groups

Question

I do not have much experience with JavaScript regex and am unsure how to only allow an input to have alphanumeric characters with a single space between groups of these characters.

Some examples of what is desirable:

"abcde"
"ab cde"
"ab c de"

Some examples of what is undesirable:

" abcde"
"abcde "
"ab   c   de"

I realize that I could use trim() to handle the first and last cases, split(" "), and then only concatenate non-empty strings but want to know how to do this with regex.

On a side note, I am fine with using \w to represent allowable characters, "_" is not a problem.

Do you want to disallow the input (ie match only the good cases), or fix the broken ones? — Robin
– Robin, Commented May 22, 2014 at 20:49

Andrew Clark · Accepted Answer · 2014-05-22 20:55:56Z

2

If you are trying to fix the bad cases, you can use something like the following:

text = text.replace(/^ +| +$|( ) +/g, "$1");

The /^ +/ will match one or more spaces at the beginning, / +$/ will match one or more spaces at the end, and /( ) +/ will match two or more spaces anywhere in the string. The capture group will be an empty string for the first two expressions but it will be a single space for ( ) + so you will replace multiple spaces with just one.

edited May 22, 2014 at 20:55

answered May 22, 2014 at 20:50

Andrew Clark

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2 Comments

asimes Over a year ago

This does work with text that has already been entered but I was hoping to do it as the text was being typed, it seems like the " +$" will not allow it, any way around this?

asimes Over a year ago

It just occurred to me that I cannot do this while it is being typed as someone will type a space for the next group of characters. I was able to change yours a bit to this replace(/^ +|( ) +/g, "$1") which allows one space at the end. Thank you for explaining

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