Using regex to extract string in javascript

Question

I am receiving strings from an external client and I am trying to perform regex-ing to extract a certain number and status that are embedded in this string. Here’s the examples of the strings that are coming in.

data = "< REP 1 INPUT_AUDIO_A ON >"
data = "< REP 1 INPUT_AUDIO_A OFF " 
data = "< REP 2 INPUT_AUDIO_A ON >" 
data = "< REP 2 INPUT_AUDIO_A OFF >"

and so on

I am trying to extract 1, 2 as gate number and the on or off as status in two different variables. I was able to extract numbers with regex as follows.

var gateNumberRegex = /[0-8]/g;
var gateNumber = data.charAt(data.search(gateNumberRegex)); //extract the gate number from string, output is 1 or 2 etc.

Not sure how to extract the on/off status, any pointers?

@GermanC Yes, it will always be there and if not, that string is not a match to perform regex-ing so I'd end up ignoring it — Cipher
– Cipher, Commented Jan 18, 2018 at 18:17
@GermanC: No need to put single expressions like \s or \w in square brackets, INPUT_AUDIO_A\s+(\w+) is equally fine and more readable. — Jan
– Jan, Commented Jan 18, 2018 at 18:28

Jan · Accepted Answer · 2018-01-18 18:32:16Z

1

Straight forward

(\d+)\s+INPUT_AUDIO_A\s+(ON|OFF)

See a demo on regex101.com.

Broken down, this says:

(\d+)         # capture 1+ digits into group 1
\s+           # match 1+ whitespaces
INPUT_AUDIO_A # INPUT_AUDIO_A literally
\s+           # 1+ whitespaces
(ON|OFF)      # ON or OFF

Use group $1 and $2, respectively as in this snippet:

var data = 'data = “< REP 1 INPUT_AUDIO_A ON >” or'
var match = data.match(/(\d+)\s+INPUT_AUDIO_A\s+(ON|OFF)/)
console.log(match[1])
console.log(match[2])

edited Jan 18, 2018 at 18:32

answered Jan 18, 2018 at 18:26

Jan

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1 Comment

Cipher Over a year ago

Super cool! Need to learn regexes. Any resources to recommend?

YakovL · Accepted Answer · 2018-01-18 18:22:16Z

1

By itself, ON/OFF may be found using /\b(ON|OFF)\b/ but if there may be ON/OFF in another place in those strings, you may go more contextual with /INPUT_AUDIO_A[\s]+(ON|OFF)/. Once you apply the regex like this

var match = `/\b(ON|OFF)\b/`.exec(yourLine)

you may extract the on/off bit with

var enabled = match ? match[1] : yourDefaultValue;

answered Jan 18, 2018 at 18:22

YakovL

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Comments

TheOdd · Accepted Answer · 2018-01-18 18:22:46Z

0

You could do something like this:

var onOrOffRegex = /INPUT_AUDIO_A ([^\s]+)/g
var onOrOff = data.match(onOrOffRegex)[1]

Then you could use the onOrOff variable to get the string status of the data.

answered Jan 18, 2018 at 18:22

TheOdd

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Comments

GalAbra · Accepted Answer · 2018-01-18 18:36:07Z

0

For your very specific case, assuming the input is "valid", this is the most straight-forward solution:

\d+|ON|OFF

Output: '1','ON','1','OFF','2','ON','2','OFF'

And then you can separate it to "pairs":

var string = document.getElementById("input").innerHTML;
var array = string.match(/\d+|ON|OFF/g);
var result = [];
var print = "";
for (i = 0; i < array.length; i += 2) {
  result += [array[i], array[i + 1]];
  print += "[" + array[i] + ", " + array[i + 1] + "]<BR>"
}

document.getElementById("input").innerHTML = print;

<div id="input">
  data = “
    < REP 1 INPUT_AUDIO_A ON>” or data = “
    < REP 1 INPUT_AUDIO_A OFF>” or data = “
    < REP 2 INPUT_AUDIO_A ON>” or data = “
    < REP 2 INPUT_AUDIO_A OFF>”
</div>

edited Jan 18, 2018 at 18:36

answered Jan 18, 2018 at 18:26

GalAbra

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Comments

jmcgriz · Accepted Answer · 2018-01-18 18:50:19Z

0

The simplest way to do this would be:

var data = "< REP 1 INPUT_AUDIO_A ON >"

var result = data.match(/\b(\d+|ON|OFF)\b/g)

This will output an array containing the number and the status: ["1", "ON"]

answered Jan 18, 2018 at 18:50

jmcgriz

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