node.js How to search for a value in an array in a string

Question

This is hard to explain so I'll just show an example. I have an array of specific keywords, like so:

const keywordArr = ['jim', 'john'];

then I have a string:

const message = 'Hello john, how are you doing today?'

I would like to check if message contains a value from keywordArr. I know I could loop through each value in keywordArr and check like this:

keywordArr.forEach(function(word) {
    if (message.toLowerCase().includes(word)) {
         rest of code here..
    }
}

However, I get around 5 messages each second, so that method would be very performance consuming. Is there any efficient way to do this?

You're either going to loop the `keywordArr` or `message` multiple times. Perhaps run some performance tests for your use-case? — , Apr 03 '18 at 17:45
you should check this first: [Multiple Pattern String Matching Algorithm](https://www.researchgate.net/publication/314191170_Single_and_Multiple_Pattern_String_Matching_Algorithm), if the min length of keywords are long, I prefer to using WM. — Sphinx, Apr 03 '18 at 17:54
If performance is all you care about and it is like to top most priority then I would suggest looking at some algorithms like these [Knuth-Morris-Pratt](https://en.wikipedia.org/wiki/Knuth%E2%80%93Morris%E2%80%93Pratt_algorithm). and [Boyer–Moore](https://en.wikipedia.org/wiki/Boyer%E2%80%93Moore_string_search_algorithm) compare them (possibly with regular expression as well) and choose accordingly. — Matus Dubrava, Apr 03 '18 at 17:54
I don't think that 5 messages per second warrants hyper-performant code. Though that certainly depends on how long your `message` is and how many keywords you have. — pushkin, Apr 03 '18 at 17:56
@pushkin 5 messages per second probably not, but this can get pretty nasty pretty quickly. — Matus Dubrava, Apr 03 '18 at 17:57
@MatusDubrava, BM and KMP is single pattern algorithm, multiple patterns should be WM or AC etc. — Sphinx, Apr 03 '18 at 17:58
I found something interesting, [PatternMatchingAlgorithms in Github](https://github.com/foo123/PatternMatchingAlgorithms) — Sphinx, Apr 03 '18 at 18:02

score 2 · Answer 1 · answered Apr 03 '18 at 18:14

2

You can use forEach() for array and match() to check string contain or not.

DEMO

const keywordArr = ['jim', 'john'],
  message = 'Hello john, how are you doing today?';

keywordArr.forEach(v => {
  if (message.match(v)) console.log(`message contain ${v}`);
});

answered Apr 03 '18 at 18:14

Narendra Jadhav

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As I said before, I wouldn't want to forEach through the array everytime as I get 5 messages a second-- and everytime the message is received, the code runs again. However, what I like about this is that it shows which word is in the array (in this case is `john`). Is there any other way to do this more efficiently? – SpecialVirusTasker Apr 03 '18 at 19:43
For other way you can aslo use [`RegExp.prototype.test()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/test). Example like this `RegExp(['jim', 'john'].join("|")).test('Hello john, how are you doing today?')` – Narendra Jadhav Apr 04 '18 at 06:14

score 1 · Answer 2 · answered Apr 03 '18 at 17:47

1

Check if the array contains any of the words using RegExp.test() (regex101 example).

const keywordArr = ['jim', 'john'];

const message = 'Hello john, how are you doing today?'

const pattern = new RegExp(`\\b${keywordArr.join('|')}\\b`, 'gi');
const contains = pattern.test(message);

console.log(contains);

answered Apr 03 '18 at 17:47

Ori Drori

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This works great iif none of the keywords contain any regex special characters. (And if the list if keywords isn't very long.) – Jordan Running Apr 03 '18 at 18:02
And you can always [escape the keywords](https://stackoverflow.com/questions/3446170/escape-string-for-use-in-javascript-regex). – Ori Drori Apr 03 '18 at 18:06

Get Off My Lawn · Accepted Answer · 2018-04-03T19:59:11.070

Return true/false

We can do this using reduce and includes, if your not into the whole RegExp thing:

const keywordArr = ['jim', 'john'];

const message = 'Hello john, how are you doing today?'

let has = keywordArr.reduce((r,v) => message.toLowerCase().includes(v.toLowerCase()) || r, false)

console.log(has)

This will match with case insensitivity. Remove both of the toLowerCaser() methods if you want a case sensitive match.

Return a name

We can modify the reduce function by adding && v which will return the value instead of a true/false value. We also will modify the starting value from false to an empty string.

const keywordArr = ['jim', 'john'];

const message = 'Hello john, how are you doing today?'

let name = keywordArr.reduce((r,v) => message.toLowerCase().includes(v.toLowerCase()) && v || r, '')

console.log(name)

Return an array of names

If we want to return a list of all names within the string, we can replace && v with && r.concat(v) then replace the starting value from an empty string to an empty array.

const keywordArr = ['jim', 'john', 'paul'];

const message = 'Hello john, how are you doing today? -- jim'

let names = keywordArr.reduce((r,v) => message.toLowerCase().includes(v.toLowerCase()) && r.concat(v) || r, [])

console.log(names)

Calling `toLowerCase()` on the same `message` in every iteration isn't doing you any favors in the performance department. — Jordan Running, Apr 03 '18 at 18:02
It could be put on the main message, but if it needs to be used somewhere else as-is, you then lose your casing. Creating a temp var would solve that though. — Get Off My Lawn, Apr 03 '18 at 18:04
This method works great, is there a way to get **which** word is in the sentence? Which in this case would be `john`, how can I let the code know that? — SpecialVirusTasker, Apr 03 '18 at 19:44
I have updated the answer with a second example that returns the string instead of a `true/false` value — Get Off My Lawn, Apr 03 '18 at 19:49

node.js How to search for a value in an array in a string

3 Answers3

Return true/false

Return a name

Return an array of names