Multiple regex replacements

Question

I receive a string with a lot of characters that I don't need and I am trying to remove them and replace them with characters that I am able to work with. My current structure has me redefining the var multiple times which I feel is not efficient and can probably be done better. Please let me know of a more effective way I can do this.

I define the date then remove the unwanted characters then append the date to the "clean" string with and underscore:

var d = Date.now()
 var article = a.replace(/ |\./g, "_")
 article = article.replace(/\r?\n|\r/g,"")
 article = article.replace(/\$|\#|\[|\]/g, "")
 article = d + "_" + article

This does work but I am curious if there is a better way.

• greybeard: See replace multiple patterns with individual replacements in one operation, esp. "the map-approach".

Answer 1

First, since you already did so inside of your two last expressions, with the same replacement:

article = article.replace(/\r?\n|\r/g,"")
article = article.replace(/\$|\#|\[|\]/g, "")

I'm puzzled why you didn't simply put both in a unique regexp:

article = article.replace(/\r?\n|\r|\$|\#|\[|\]/g, "")

Then to integrate with the 1st one, you might choose to:

• join the two distincts replacements in a single line:

  var article = a.replace(/ |\./g, "_").replace(/\r?\n|\r|\$|\#|\[|\]/g, "")
  

• or use a map approach, either suche the one pointed by @greybeard's link, or like this way (even if it might look a bit too sohpisticated for only two cases):

  var replacements = new Map([
   [/ |\./g, '_'],
   [/\r?\n|\r|\$|\#|\[|\]/g, '']
   ]),
   article = a;
  replacements.forEach(function(value, key){
   article = article.replace(key, value);
   });
  

The most interesting aspect in this latter solution is that it may be easily expanded if more replacements are needed.

---

EDIT following a good suggestion from @Niet the Dark Absol.

As soon as there are several unique characters to look for, with the same replacement, this kind of regexp /(a|b|c)/ can be replaced by /[abc]/, which is both simpler and more efficient!

Any of the above proposed solutions can be improved this way, so the latter one becomes:

 var replacements = new Map([
 [/[ .]/g, '_'],
 [/[\r\n$#[\]]/g, '']
 ]),
 article = a;
 replacements.forEach(function(value, key){
 article = article.replace(key, value);
 });

• Niet the Dark Absol: I would suggest improving that regex further. /[\r\n\[\]$#]/g is much more concise and works in the same way, and can have other options added to it easily enough.
• cFreed: @NiettheDarkAbsol Indeed you're right, and I should have noticed that! I'll edit my answer about that. Thanks!

Answer 2

You could define your pattern and replacement in an array. Then you can use reduce to carry the string through the array while replacing them.

let formatters= [
 {pattern: / |\./g, replacement: '_'},
 {pattern: /\r?\n|\r/g, replacement: ''},
 {pattern: /\$|\#|\[|\]/g, replacement: ''},
];
let article = formatters.reduce((a, f) => a.replace(f.pattern, f.replacement), a);

• greybeard: While this cleanly separates pairing patterns and replacements from using them in replace, it almost hides the time complexity of (avoidably) applying replace more than once.