JavaScript RegEx to replace words starting with # in a string

Question

I am using the below function to replace words beginig with # from the string, with variables of exact same name from the extra_data object.

var messageString = "The folder #folder_name was removed from the workspace #workspace_name by #user_name"
var re = /(?:^|\W)#(\w+)(?!\w)/g, match;
while (match = re.exec(messageString)) {
  messageString = messageString.replace(match[0],extra_data[match[1]]);
  console.log("I am here--------------------------------------------->1");
  console.log(messageString);
}

Console log

I am here--------------------------------------------->1
The folder23545 was removed from the workspace #workspace_name by #user_name
I am here--------------------------------------------->1
The folder23545 was removed from the workspace127 by #user_name

The above code replaces only 2 instances and sometimes eats up white space also as you can see at workspace127. What am i doing wrong?

What is the point of that lookahead?

tenub
– tenub

2014-01-14 14:39:41 +00:00
Commented Jan 14, 2014 at 14:39 — tenub
– tenub, Commented Jan 14, 2014 at 14:39
Just use thg435's solution. It makes the most sense to me.

tenub
– tenub

2014-01-14 14:47:51 +00:00
Commented Jan 14, 2014 at 14:47 — tenub
– tenub, Commented Jan 14, 2014 at 14:47

georg · Accepted Answer · 2014-01-14 14:46:13Z

6

I guess replace will be more suitable here:

result = messageString.replace(/#(\w+)/g, function(_, $1) { return extra_data[$1] })

or, to replace only words that start with #:

.replace(/(^|\W)#(\w+)/g, function(_, $1, $2) { return $1 + extra_data[$2] })

answered Jan 14, 2014 at 14:46

georg

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1 Comment

epascarello Over a year ago

I probably would have a check to make sure that there is a value. +1

OnlyThenDidIReckonMyCurse · Accepted Answer · 2014-01-14 14:55:09Z

1

You are changing the string inside the loop. re.exec uses a lastIndex attribute to store where to start the next match. When you replace "#workspace_name" with "127", messageString gets shorter.
You are consuming space at the beginning.

I think this should do it:

var messageString = "The folder #folder_name was removed from the workspace #workspace_name by #user_name"
var re = /(^|\W)#(\w+)/g, match;
var changedString = messageString;
while (match = re.exec(messageString)) {
    changedString = changedString.replace(match[0], match[1] + extra_data[match[2]]);
}

edited Jan 14, 2014 at 14:55

answered Jan 14, 2014 at 14:47

OnlyThenDidIReckonMyCurse

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