javascript将所有出现的“，\\ S”替换为“，\\ S”

Question

I want to have spaces separating items in a CSV string. That is "123,456,789" => "123, 456, 789". I have tried, but been unable to construct a regexp to do this. I read some postings and thought this would to the trick, but no dice.

 text = text.replace(new RegExp(",\S", "g"), ", ");

Could anyone show me what I am doing wrong?

Answer 1

You have two problems:

1. Backslashes are a pain in the, um, backslash; because they have so many meanings (eg to let you put a quote-mark inside a string), you often end up needing to escape the backslash with another backslash, so you need ",\\\\S" instead of just ",\\S" .
2. The \\S matches a character other than whitespace , so that character gets removed and replaced along with the comma. The easiest way to deal with that is to "capture" it (by putting it in parentheses), and put it back in again in the replacement (with $1 ).

So what you end up with is this:

text = text.replace(new RegExp(',(\\S)', "g"), ", $1");

However, there is a slightly neater way of writing this, because JavaScript lets you write a regex without having a string, by putting it between slashes. Conveniently, this doesn't need the backslash to be escaped, so this much shorter version works just as well:

text = text.replace(/,(\S)/g, ", $1");

As an alternative to capturing, you can use a "zero-width lookahead", which in this situation basically means "this bit has to be in the string, but don't count it as part of the match I'm replacing". To do that, you use (?=something) ; in this case, it's the \\S that you want to "look ahead to", so it would be (?=\\S) , giving us this version:

text = text.replace(/,(?=\S)/g, ", ");

Answer 2

There are 2 mistakes in your code:

1. \\S in a string literal translates to just S , because \\S is not a valid escape sequence. As such, your regex becomes /,S/g , which doesn't match anything in your example. You can escape the backslash ( ",\\\\S" ) or use a regex literal ( /,\\S/g ).

2. After this correction, you will replace the character following the comma with a space. For instance, 123,456,789 becomes 123, 56, 89 . There are two ways to fix this:

   1. Capture the non-space character and use it in the replacement expression:

       text = text.replace(/,(\\S)/g, ', $1') 

   2. Use a negative lookahead assertion (note: this also matches a comma at the end of the string):

       text = text.replace(/,(?!\\s)/g, ', ') 

Answer 3

text = text.replace(/,(\S)/g, ', $1');

Answer 4

try this:

var x = "123,456,789";
x = x.replace(new RegExp (",", "gi"), ", ");