Argthtjtr

Let's say I have an array of strings, and I need specific info from them, what would be an easy way to do that?

Suppose the array was this

let infoArr = [

  "1 Ben Howard 12/16/1988 apple",

  "2 James Smith 1/10/1999 orange",

  "3 Andy Bloss 10/25/1956 apple",

  "4 Carrie Walters 8/20/1975 peach",

  "5 Doug Jones 11/10/1975 peach"

];

Let's say I wanted the date extracted and saved into another array, well I could make a function like this

function extractDates(arr){

  let dateRegex = /(d{1,2}/){2}d{4}/g, dates = "";

  let dateArr = ;

  for(let i = 0; i<arr.length; i++){

    dates = /(d{1,2}/){2}d{4}/g.exec(arr[i])

    dates.pop();

    dateArr.push(dates);

  }

  return dateArr.flat();

}

Although this works, it is clunky and requires I pop() because it will return an array of arrays, ie: ["12/16/1988", "16/"], plus I need to call flat afterwards.

Another option would be to substring the strings, with a given position, where I need to know a regex pattern.

function extractDates2(arr){

  let dates = ;

  for(let i = 0; i<arr.length; i++){

    let begin = regexIndexOf(arr[i], /(d{1,2}/){2}d{4}/g);

    let end = regexIndexOf(arr[i], /[0-9] /g, begin) + 1;

       dates.push(arr[i].substring(begin, end));

  }

  return dates;

 }

And of course have a regexIndexOf function

function regexIndexOf(str, regex, start = 0){

  let indexOf = str.substring(start).search(regex);

  indexOf = (indexOf >= 0) ? (indexOf + start) : -1;

  return indexOf;

}

Again this function also works, but it seems like an awful lot just to extract something simple. Is there an easier way to extract data into an array?

One option would be to join the strings by a separator that won't be matched, like ,, then just perform the global match to get an array of dates from it:

let infoArr = [

  "1 Ben Howard 12/16/1988 apple",

  "2 James Smith 1/10/1999 orange",

  "3 Andy Bloss 10/25/1956 apple",

  "4 Carrie Walters 8/20/1975 peach",

  "5 Doug Jones 11/10/1975 peach"

];

const result = infoArr

  .join(',')

  .match(/(d{1,2}/){2}d{4}/g);

console.log(result);

One approach could be using map() over the elements of the array applying the match on each element, and finally call flat() to get the desired result:

let infoArr = [

  "1 Ben Howard 12/16/1988 apple",

  "2 James Smith 1/10/1999 orange",

  "3 Andy Bloss 10/25/1956 apple",

  "4 Carrie Walters 8/20/1975 peach",

  "5 Doug Jones 11/10/1975 peach"

];



const result = infoArr.map(o => o.match(/(d{1,2}/){2}d{4}/g)).flat();



console.log(result);

Alternatively, you could use flatMap():

let infoArr = [

  "1 Ben Howard 12/16/1988 apple",

  "2 James Smith 1/10/1999 orange",

  "3 Andy Bloss 10/25/1956 apple",

  "4 Carrie Walters 8/20/1975 peach",

  "5 Doug Jones 11/10/1975 peach"

];



const result = infoArr.flatMap(o => o.match(/(d{1,2}/){2}d{4}/g));



console.log(result);

Also, if you need to remove null values from the final array in the case there are strings without dates, you can apply filter(), like this:

const result = infoArr.map(o => o.match(/(d{1,2}/){2}d{4}/g))

                      .flat()

                      .filter(date => date !== null);



const result = infoArr.flatMap(o => o.match(/(d{1,2}/){2}d{4}/g))

                      .filter(date => date !== null);

Example (taking into consideration some conflicting data)

let infoArr = [

  "1 Ben Howard 12/16/1988 apple 10/22/1922",

  "2 James Smith orange",

  "3 Andy Bloss 10/25/1956 apple",

  "4 Carrie Walters 8/20/19075 peach",

  "5 Doug Jones 11/10-1975 peach"

];



const result = infoArr.flatMap(o => o.match(/(d{1,2}/){2}d{4}/g))

                      .filter(date => date !== null); /* or filter(date => date) */



console.log(result);

Although this works, it is clunky and requires pop() because it will return an array of arrays, ie: ["12/16/1988", "16/"], plus I need to call flat afterwards.

The regex exec method always has its match in the 0 property (assuming that it matches at all), you can just access that and push it to your array:

let infoArr = [

  "1 Ben Howard 12/16/1988 apple",

  "2 James Smith 1/10/1999 orange",

  "3 Andy Bloss 10/25/1956 apple",

  "4 Carrie Walters 8/20/1975 peach",

  "5 Doug Jones 11/10/1975 peach"

];



function extractDates(arr){

  const dateRegex = /(d{1,2}/){2}d{4}/g;

  const dateArr = ;

  for (const str of arr){

    const date = /(d{1,2}/){2}d{4}/g.exec(str);

    dateArr.push(date[0]);

  }

  return dateArr;

}



console.log(extractDates(infoArr));

(of course you could also do the same in a map callback)

You can use reduce() rather than the loops to pair down the code. Just be careful to keep the null out of the array if there is no match.

let infoArr = [

    "1 Ben Howard 12/16/1988 apple",

    "2 James Smith 1/10/1999 orange",

    "3 Andy Bloss 10/25/1956 apple",

    "4 Carrie Walters 8/20/1975 peach",

    "5 Doug Jones 11/10/1975 peach"

  ];

  

let regex = /(d{1,2}/){2}d{4}/g

let dates =  infoArr.reduce((arr, s) => arr.concat(s.match(regex) || ) , )

console.log(dates)