array.pop() dont return seem to return the object when call in a anonymous function. (with RegExp)

Question

Sorry if the question already get answered somewhere, but i dont find anything for this specific issue online.

I'm trying to create an array of RegExp and apply them after to filter an array. But I can pop and use my regex directly in the anonymous filter function.

As you can see bellow it only dont work in this specific configuration. (I don't try with other object than RegExp yet).

var regex = [new RegExp("01$"), new RegExp("01$")];
  var arr = ["001","02","012", "12301"];
  var take = regex.pop();
  //work
  console.log(arr.filter( a=> a.match(take)));
  console.log(arr.filter( a=> a.match(new RegExp("01$"))));
  console.log(arr.filter( a=> a.match(regex[0])));
  
  //don't
  console.log(regex)
  console.log(arr.filter( a=> a.match(regex.pop())));
  console.log(regex)

Before I continue to test and undertand this behaviour i would like your inputs to know if i miss something obvious.

Thanks in advance

In the second version, the arrow function is called multiple times, so pop is executed multiple times — Nick Parsons, Jun 29 '20 at 12:08
Note that your `regex` array is shorter than `arr`. So by the time you hit the 3rd element in your array, `regex` will be empty. — Evan Trimboli, Jun 29 '20 at 12:10
The answer is at https://stackoverflow.com/a/38075457/3832970 — Wiktor Stribiżew, Jun 29 '20 at 13:45

score 0 · Answer 1 · answered Jun 29 '20 at 12:12

0

Assume you want to check each item matches any of the regular expressions, you can do this:

const matches = arr.filter(a => regex.some(r => r.test(a)));

answered Jun 29 '20 at 12:12

Evan Trimboli

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`some()` is a good idear to apply all the regex at once. – Julien Maret Jun 29 '20 at 12:21

array.pop() dont return seem to return the object when call in a anonymous function. (with RegExp)

1 Answers1