Discussion on: Why this regex it's not working properly? [solved]

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you can do like this:

const foodList = ["apple", "soap", "banana", "watermelon", "pizza"];

let fruitList = []
function getFruits(foodList) {
  const fruitRGX = /apple|banana|watermelon/g;
  foodList.forEach(food =>{
      if(food.match(fruitRGX)){
        fruitList.push(food)
      }
  })

  return fruitList
}

console.log(getFruits(foodList))
// output: ["apple", "banana", "watermelon"]

I think if you use match(regex) instead of test() is better.
and you can use array.forEach() instead of for() for better readability!

Gil Rudolf Härdi • Aug 29 '21

Thanks for the advise, what I really need is to know what happened with my code.

What is the reason for not output watermelon?

But somehow your code is very helpful, you used match and it worked well so my question has changed to why test don't worked but match yes?. This time I found the info that I want:
The RegEx object has a property called lastIndex updated with test method, that property don't reset when test returns true. If the same regex is used again then can happen what happened with my code.

Yogesh Chavan • Aug 29 '21

@ghaerdi I have explained this weird behavior of test method in my this article.

Federico Vázquez • Aug 29 '21

Or better yet, a pure function:

const knownFruits = new Set(["apple", "banana", "watermelon"])

function getFruits(foodList) {
  return foodList.filter(food => knownFruits.has(food))
}