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?

score 0 · Accepted Answer · edited May 23 '17 at 11:46

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.

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? — Trav Easton, Jun 30 '16 at 06:07
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, Jun 30 '16 at 16:18
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: http://stackoverflow.com/questions/33234666/how-to-map-reduce-filter-a-set-in-javascript. Anyways, I updated my answer with an example that reduces a set. — ccnokes, Jun 30 '16 at 16:30

Trav Easton · Answer 2 · 2017-02-20T06:51:18.690

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 '17 at 06:51

answered Jun 30 '16 at 10:05

Trav Easton

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Javascript Regex for each item in Set

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