Javascript - How to concatenate string values from two arrays of different sizes?

Question

I have two arrays, for example:

Array1:

arr1 = ["Precon", "Contra", "Postco", "Cancel", "Consul"]

Array2:

arr2 = ["EJID", "EMBA", "EMPR", "GOBI", "PART", "PPOL", "SACI", "SOFL", "SOFM", "0000", "", "0002", "0003", "0004", "0005", "0006", "0007", "0008", "0009", "0010", "0011", "0012", "0013", "0014", "0015", "0016", "011", "0110", "9999"]

I want to generate a new array from two above concatenating the individual items into new items recursively for each one in array1, to get a final array like this:

final = ['Precon-EJID', 'Contra-EJID', 'Postco-EJID', 'Cancel-EJID', 'Consul-EJID', 'Precon-EMBA', 'Contra-EMBA', 'Postco-EMBA', 'Cancel-EMBA', 'Consul-EMBA', 'Precon-EMPR', 'Contra-EMPR', 'Postco-EMPR', 'Cancel-EMPR', 'Consul-EMPR'...etc]

Thank you in advance

Possible duplicate of Cartesian product of multiple arrays in JavaScript — pwolaq
– pwolaq, Commented Jan 23, 2018 at 22:21
What have you tried? This can be done with a number of different loop approaches — charlietfl
– charlietfl, Commented Jan 23, 2018 at 22:21
The multiple answers posted to this Question prove that the "downvote" and "close" vote standards and rationales, if any, are fully arbitrary and capricious. Which is ok. Just be aware that it is duly noted if any of the users whom answered this Question find the audacity to post a comment questioning this users' answering any question here at SO whatsoever. None of the users whom posted answers to this question should vote to close another question under the premise of "off-topic because -> ("why isn't this code working?")" else that vote is fraudulent even if only you know that fact — guest271314
– guest271314, Commented Jan 23, 2018 at 22:45

Blue · Accepted Answer · 2018-01-23 22:22:01Z

4

You can do this with 2 simple for of loops:

var arr1 = ["Precon", "Contra", "Postco", "Cancel", "Consul"];

var arr2 = ["EJID", "EMBA", "EMPR", "GOBI", "PART", "PPOL", "SACI", "SOFL", "SOFM", "0000", "", "0002", "0003", "0004", "0005", "0006", "0007", "0008", "0009", "0010", "0011", "0012", "0013", "0014", "0015", "0016", "011", "0110", "9999"]

var finalArr = [];

for ( var item2 of arr2 ) {
  for ( var item1 of arr1 ) {
    finalArr.push(`${item1}-${item2}`);
  }
}

console.log(finalArr);

answered Jan 23, 2018 at 22:22

Blue

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Comments

Ori Drori · Accepted Answer · 2018-01-23 22:24:15Z

2

You can use nested Array#map calls, and flatten the results using Array#concat:

const arr1 = ["Precon", "Contra", "Postco", "Cancel", "Consul"]

const arr2 = ["EJID", "EMBA", "EMPR", "GOBI", "PART", "PPOL", "SACI", "SOFL", "SOFM", "0000", "", "0002", "0003", "0004", "0005", "0006", "0007", "0008", "0009", "0010", "0011", "0012", "0013", "0014", "0015", "0016", "011", "0110", "9999"]

const result = [].concat(...arr2.map((s1) => arr1.map((s2) => `${s2}-${s1}`)))

console.log(result)

edited Jan 23, 2018 at 22:24

answered Jan 23, 2018 at 22:21

Ori Drori

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1 Comment

Blue Over a year ago

Solid answer. It's a little messy having to use the new spread syntax (...), but works and doesn't require a third "building array".

CRice · Accepted Answer · 2018-01-23 22:31:12Z

0

Here's a one liner to do this:

arr1 = ["Precon", "Contra", "Postco", "Cancel", "Consul"]
arr2 = ["EJID", "EMBA", "EMPR", "GOBI", "PART", "PPOL", "SACI", "SOFL", "SOFM", "0000", "", "0002", "0003", "0004", "0005", "0006", "0007", "0008", "0009", "0010", "0011", "0012", "0013", "0014", "0015", "0016", "011", "0110", "9999"]

const result = [].concat(...arr1.map(prefix => arr2.map(suffix => prefix+suffix)));
console.log(result)

// EDIT: if order matters, reverse the use of arr1 and arr2:

const orderedResult = [].concat(...arr2.map(suffix => arr1.map(prefix => prefix+suffix)));
console.log(orderedResult)

edited Jan 23, 2018 at 22:31

answered Jan 23, 2018 at 22:23

CRice

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11 Comments

pwolaq Over a year ago

why [].concat?

Jaromanda X Over a year ago

your output does not match desired output :p

CRice Over a year ago

Flattens the array so that all items are at the same level. Without it, the result would be a 2-dimensional array: [["PreconEJID", ...], ["ContraEJID", ...], ...]

CRice Over a year ago

@JaromandaX I though it did? In what way? OP's final array is not nested. Or do you mean the order is incorrect?

guest271314 Over a year ago

@CRice OP does not specify any particular ordering of the result

|

Aluan Haddad · Accepted Answer · 2018-01-23 22:40:02Z

0

const prefixes = [
  "Precon",
  "Contra",
  "Postco",
  "Cancel",
  "Consul"
];

const suffixes = [
  "EJID", "EMBA", "EMPR",
  "GOBI", "PART", "PPOL",
  "SACI", "SOFL", "SOFM",
  "0000", "", "0002",
  "0003", "0004", "0005",
  "0006", "0007", "0008",
  "0009", "0010", "0011",
  "0012", "0013", "0014",
  "0015", "0016", "011",
  "0110", "9999"
];

const results = suffixes
  .map(suffix => prefixes.map(prefix => prefix + '-' + suffix))
  .reduce((xs, ys) => [...xs, ...ys]);

console.log(results);

edited Jan 23, 2018 at 22:40

answered Jan 23, 2018 at 22:33

Aluan Haddad

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2 Comments

Blue Over a year ago

There should be dashes between the prefix/suffixes

guest271314 Over a year ago

@FrankerZ If we are positing what "should be". There should first be a modicum of effort put forth by OP to resolve their own inquiry, which is wholly absent from the Question.

Get Off My Lawn · Accepted Answer · 2018-01-23 22:42:04Z

0

Another option is to use reduce...

let arr1 = ["Precon", "Contra", "Postco", "Cancel", "Consul"]

let arr2 = ["EJID", "EMBA", "EMPR", "GOBI", "PART", "PPOL", "SACI", "SOFL", "SOFM", "0000", "", "0002", "0003", "0004", "0005", "0006", "0007", "0008", "0009", "0010", "0011", "0012", "0013", "0014", "0015", "0016", "011", "0110", "9999"]

let arr3 = arr2.reduce((arr, val) => {
    let f = []
    arr1.forEach(itm => val && f.push(itm + '-' + val))
    return arr.concat(f)
}, [])

console.log(arr3)

answered Jan 23, 2018 at 22:42

Get Off My Lawn

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Comments

Jimenemex · Accepted Answer · 2018-01-23 22:58:10Z

Here's a recursive one. Just like the OP asked. Took me a while. :P

arr1 = ["Precon", "Contra", "Postco", "Cancel", "Consul"]

arr2 = ["EJID", "EMBA", "EMPR", "GOBI", "PART", "PPOL", "SACI", "SOFL", "SOFM", "0000", "", "0002", "0003", "0004", "0005", "0006", "0007", "0008", "0009", "0010", "0011", "0012", "0013", "0014", "0015", "0016", "011", "0110", "9999"]

var arr = [];

console.log(concat(arr1, arr2, 0, 0, 0));

function concat(arr1, arr2, arrIndex, index1, index2) {
  //console.log(arr1.length);
  if (index2 === (arr2.length)) {
    return;
  } else {
    arr[arrIndex] = arr1[index1] + '-' + arr2[index2];
    if (index1 !== (arr1.length - 1)) {
      index1++;
    } else if (index1 === (arr1.length - 1)) {
      index1 = 0;
      index2++;
      //concat(arr1, arr2, ++arrIndex, index1, index2++); // Not here dummy :P
    }
    concat(arr1, arr2, ++arrIndex, index1, index2++);
  }
  return arr;
}

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