Replace standalone string with regex in Javascript

Question

I am trying to write a function to replace any standalone set of matching characters. For example:

var myarray = ["this is", "this is iss"]
var my2array = []
var regex = '/bis/b'

for (const i of myarray) {
  var x = i.replace(regex, "")
  my2array.push(x)
}

console.log(my2array)

My desired output would be:

["this", "this iss"]

I got this working in Python, but am not able to translate it properly to Javascript. Currently my output is just the array values [0] and [1] (not sure why Javascript is doing that).

Anyway, my question is, how can I achieve the desired output using regex in Javascript?

You're iterating over the array indexes, not the array values. — Barmar
– Barmar, Commented Jul 9, 2019 at 21:20
None of your strings contain bis, why do you expect it to replace anything? — Barmar
– Barmar, Commented Jul 9, 2019 at 21:22

benvc · Accepted Answer · 2019-07-09 21:33:58Z

3

You are misunderstanding the regex syntax (forward slashes indicate the start and end of the expression, backslashes are used with various characters to indicate certain character sets). You could replace your regex with the following since I think you intended your regex to replace instances of "is" with word boundaries on either side:

var regex = /\bis\b/

edited Jul 9, 2019 at 21:33

answered Jul 9, 2019 at 21:24

benvc

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Comments

blhsing · Accepted Answer · 2019-07-09 21:46:39Z

1

@benvc's answer is close but leaves extra spaces after replacements, and therefore does not match the desired output.

You can instead use an alternation of two patterns, one that deals with scenarios with spaces on both sides of is (in which case you can use a positive lookahead pattern to avoid matching the last space to allow leaving a space between words after replacement), and the other that deals with scenarios with spaces on only one side of is, or none at all:

var myarray = ["this is", "this is iss", "is this", "is"]
var my2array = []
var regex = /\s+is\s*(?=\s)|\s*\bis\b\s*/

for (const i of myarray) {
  var x = i.replace(regex, "")
  my2array.push(x)
}

console.log(my2array)

edited Jul 9, 2019 at 21:46

answered Jul 9, 2019 at 21:26

blhsing

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Comments

Barmar · Accepted Answer · 2019-07-09 21:26:03Z

0

this is not the solution but a working example:

var myarray = ["this is", "this is iss"];
var my2array = [];
var regex = /is/g;

for (const i in myarray) {
  var x = myarray[i].replace(regex, "")
  my2array.push(x)
}

console.log(my2array)

edited Jul 9, 2019 at 21:26

Barmar

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answered Jul 9, 2019 at 21:20

fredericrous

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5 Comments

find_all Over a year ago

Getting this: Error: Cannot read property 'replace' of undefined

Barmar Over a year ago

@find_all This answer was written before you changed in to of.

Barmar Over a year ago

This doesn't produce the desired output, because you're not matching word boundaries.

fredericrous Over a year ago

yup just giving a working example of the use of regex here

find_all Over a year ago

Thanks for this, although this is the output I was getting before, using replace without regex. Barmar is correct in that I am specifically looking looking for standalone strings to be replaced.

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