Using a variable inside RegEx

Asked Oct 12 '15 at 15:40

Active Oct 12 '15 at 15:40

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var newWord = prompt("What word do you want to block?");
var myRegExp = new RegExp("\b" + newWord + "\b", "ig");
var myString = "This is a test. To replace the word test with something other than test.";

function replaceString(string) {
  var newString = string.replace(myRegExp, "**");
  document.getElementById("output").innerHTML = newString;
}

replaceString(myString);

I am practicing with RegEx's and have been stumped. This is just a sample of the type of code I am trying to write. Essentially, I want to take input from a prompt and store that in the newWord variable. I then use that variable inside a RegEx and then replace that value of that RegEx (for example the word "test") with "**".

I have no problem with this code when I just use new RegExp(newWord, "ig");. The problem arises when I try to add word boundaries around the variable. I have tried multiple ways and have searched for the answer but have come up dry. Would anyone be able to explain what I am doing wrong? Thanks!

asked Oct 12 '15 at 15:40

Tyler Hines

5

You need to double-escape the slashes, `new RegExp("\\b" + newWord + "\\b", "ig");`. Also, if the word contain special characters, they need to be escaped as well. – Tushar Oct 12 '15 at 15:41
@Tushar That should really be an answer :) – Luaan Oct 12 '15 at 15:42
2

It is a millionth dupe. This post must be closed. – Wiktor Stribiżew Oct 12 '15 at 15:42
Huh, I could have sworn I tried this! I guess I didn't! Thanks, that fixed the problem. – Tyler Hines Oct 12 '15 at 15:42
@TylerHines For explanation you can see first part of http://stackoverflow.com/a/32891691/2025923 – Tushar Oct 12 '15 at 15:47

Using a variable inside RegEx

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