JavaScript: how to filter a string array based on a boolean array [duplicate]

Question

I am a newbie to JavaScript, and now trying to find a way to filter a string array based on a boolean array.

Given

arr1 = ["Apple", "Banana", "Orange"]
arr2 = [false, true, false]

The expected output is:

["Banana"]

I tried

arr1.filter(item => arr2[item])

but it didn't work. Could you please figure out where I was wrong and what could be a better solution. Your answers will be highly appreicated.

See How much research effort is expected of Stack Overflow users?. The documentation immediately reveals what item is and console.log(arr2[item]) would immediately reveal why this doesn’t work. And the linked question can be found by literally typing your exact title into Google (second result). — Sebastian Simon
– Sebastian Simon, Commented Nov 23, 2022 at 2:00

flyingfox · Accepted Answer · 2022-11-23 01:27:06Z

2

You can get the index in filter(),then check the value in arr2

let arr1 = ["Apple", "Banana", "Orange"]
let arr2 = [false, true, false]

let result = arr1.filter((e,i) => arr2[i])
console.log(result)

answered Nov 23, 2022 at 1:27

flyingfox

13.5k4 gold badges30 silver badges43 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Thanks for your prompt answer, which really helps me a lot. May I ask what kind of role "e" play here since it has not been used?

@WenMa e is the iterate element and i is the iterate element index,see the picture or official document,you will find it