Javascript Regex OR doubts

Question

I'd like to clarify two doubts about javascript Regexs.

Is it possible to nest a second OR expression inside a primary one, as below (v|b|c):
```
/(value1|value2|value3|(v|b|c)alue4)/
```
Is it possible to break lines into the same expression, as below (in order to be more readable):
```
/(value1|
  value2|
  value3|
  (v|b|c)alue4)
/
```

Thanks so much

For part1, have you tried it out? /(value1|value2|value3|(v|b|c)alue4)/.test("balue4") — David Sherret
– David Sherret, Commented Feb 24, 2015 at 17:09

James Donnelly · Accepted Answer · 2015-02-24 17:14:44Z

4

Why don't you try it yourself?

/(value1|value2|value3|(v|b|c)alue4)/.test("calue4")

-> true

/(value1|
  value2|
  value3|
  (v|b|c)alue4)
/.test("calue4")

->  Uncaught SyntaxError: Invalid regular expression: missing /

If you really want to use that multi-line style, you can always use string concatenation and the RegExp object:

new RegExp("(value1|" +
           "value2|" +
           "value3|" +
           "(v|b|c)alue4)").test("calue4")

-> true

answered Feb 24, 2015 at 17:09

James Donnelly

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Comments

Jonathan · Accepted Answer · 2015-02-24 17:21:10Z

3

To expand on James answer; you can also escape newlines in a string instead of concatenating several strings.

new RegExp("(value1|\
value2|\
value3|\
(v|b|c)alue4)").test("calue4")

Does it make it more readable and should you do this? No

Warning, this will incorporate white-space between \ and the start of the next character.

answered Feb 24, 2015 at 17:21

Jonathan

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Wait, there's something wrong with this, it logs false

Ah, the preceding whitespace was incorporated in the line since we escaped the newline.