Javascript Regex for each item in Set

Question

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set

I have a Set with a whole bunch of things but I want to regex (or just check if part of a string exists) in the set.

I was thinking something like this.

mySet = new Set(["foo", "bar", "something SomethingIWant somethingelse"]);

/SomethingIWant/.test(mySet);
// false

mySet.forEach(myRegex(/SomethingIWant/));
// Doesn't work as I expect

Basically I need a function to iterate over a set(that I specify), regex testing each item (with a regex that I specify).

Does javascript allow this?

Community · Accepted Answer · 2017-05-23 11:46:11Z

0

Yes, it looks like you are on the right track. This works for me:

let mySet = new Set(["foo", "bar", "something SomethingIWant somethingelse"]);

mySet.forEach(item => console.log( /SomethingIWant/.test(item) ) ); //returns false, false, true

// another way to accomplish the same thing
for(let item of mySet) {
  console.log( /SomethingIWant/.test(item) );
}

Some references: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set (see "Iterating Sets" section) https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set/forEach

Here's a more specific answer to your question:

function reduceSet(mySet, f, initial) {
    var result = initial;
    for (var v of mySet) result = f(result, v);
    return result;
}

reduceSet(mySet, (aggr, item) => {
    aggr = /SomethingIWant/.test(item);
    return aggr;
});
// => true

Set reduce implementation borrowed from: How to map/reduce/filter a Set in JavaScript?

I personally don't like modifying the prototypes of core JS objects, so I made it it's own function. However, it looks like reduce for Sets is slated for ES7 so you could safely polyfill it.

edited May 23, 2017 at 11:46

CommunityBot

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answered Jun 30, 2016 at 5:14

ccnokes

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3 Comments

Trav Easton Over a year ago

That was excellent, thanks. In trying to make it a function, the mySet.forEach(item => console.log( /SomethingIWant/.test(item) ) ); line returns undefined, do you have any idea why?

ccnokes Over a year ago

because forEach returns undefined. Looking at your code below, what you really want is reduce but Set doesn't have a reduce method unfortunately. @TravEaston

ccnokes Over a year ago

Oh silly me, some would probably be better for your use case than reduce. An example implementation of some on a Set is also available here: stackoverflow.com/questions/33234666/…. Anyways, I updated my answer with an example that reduces a set.

Trav Easton · Accepted Answer · 2017-02-20 06:51:18Z

0

Finally figured it out with @ccnokes solution but wanted to provide my final result.

Set.prototype.regex = function(regex) {
    for(const item of this) {
       if (regex.test(item)) return true;
    }
    return false;
}

let mySet = new Set(["foo bar", "baz qux bar"]);

mySet.regex(/nothing/); // false
mySet.regex(/qux/);     // true

edited Feb 20, 2017 at 6:51

answered Jun 30, 2016 at 10:05

Trav Easton

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