How to get particular part of string from an array of strings using javascript?

Question

Hi below is array of strings

const arr = [
    "list/1/item/1/",
    "some-domain/2/item/2/",
    "item/3/",
    "some-domain/4/item/5/subitem/1/",
]

i have to filter those strings that start with string "item/3/" or ends with string "item/3/"

so from above array expected filtered array is like below,

const filtered_arr = [
    "list/1/item/1/",
    "some-domain/2/item/2/",
    "item/3/",
]

from the filtered array i want to get the number after "/item/". so from above filtered array the expected output is

const arr_ids = ["1", "2", "3"]

what i have tried,

i have used below to match those strings that start or end with /item/3/

const filtered_arr = arr.map(str) => {
    return str.match(/item\/[0-9](\/)?$/g);
}

this gives the filtered_arr

const filtered_arr = [
    "list/1/item/1/",
    "some-domain/2/item/2/",
    "item/3/",
]

but how do i map through each array item and get the number after string "/item/".

could someone help me with this. thanks.

"i have used below to match those strings that start or end with /item/3" but you are not checking 3 explicitly? — cmgchess
– cmgchess, Commented Feb 6, 2022 at 11:54
Your expected filtered array doesn't make sense. How is item/3/ in that list? That clearly starts with item/3/, which you explicitly ruled out. — connexo
– connexo, Commented Feb 6, 2022 at 11:55
the number after item/ can be anything. like 3, 1 or any number — stackuser
– stackuser, Commented Feb 6, 2022 at 11:55
The question states i have to filter those strings that start with string "item/3/" or ends with string "item/3" and we find element item/3 which is not even present in the original array (the original array's element is item/3/). Please note: item/3 is NOT item/3/. These are different strings. — jsN00b
– jsN00b, Commented Feb 6, 2022 at 12:00
sorry for the typo i have edited the array and the expected output — stackuser
– stackuser, Commented Feb 6, 2022 at 12:00

Tim Biegeleisen · Accepted Answer · 2022-02-06 12:03:40Z

1

Use filter to filter paths either starting or ending in item/\d+/. Then use map to extract the item number from each matching path.

const arr = [
    "list/1/item/1/",
    "some-domain/2/item/2/",
    "item/3/",
    "some-domain/4/item/5/subitem/1",
];
var output = arr.filter(x => x.match(/^item\/\d+|\bitem\/\d+\/$/))
                .map(x => x.match(/(?<=^item\/)\d+|(?<=\bitem\/)\d+(?=\/$)/)[0]);
console.log(output);

edited Feb 6, 2022 at 12:03

answered Feb 6, 2022 at 11:57

Tim Biegeleisen

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4 Comments

stackuser Over a year ago

thanks but says object could be possibly null on map function

Tim Biegeleisen Over a year ago

Your data has some problem. My code is working with the sample data you actually provided.

stackuser Over a year ago

yes there was a problem with the way i filter. now it works.

stackuser Over a year ago

but this seems to also match the strings where the string item/3/ is followed by other string. for example it shouldnt match strings like "item/3/subitem/1" . meaning string item/3/ shouldnot be matched if its followed by another string. it can match only if its starts with item/3/ and has no following string or ends with item/3/. thanks

NullVoid · Accepted Answer · 2022-02-06 12:01:22Z

1

This may help:

const filtered_arr = arr.map(str) => {
    const match = str.match(/\/item\/(\d)/);
    return(match[1]);
}

answered Feb 6, 2022 at 12:01

NullVoid

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