Javascript search in multidimensional array by value?

Question

I have a multidimensional array like this

(2) ["Vårt solsystem är 4,5 miljarder år gammalt.", "vart-solsystem-ar-45-miljarder-ar-gammalt"]
0: "Vårt solsystem är 4,5 miljarder år gammalt."
1: "vart-solsystem-ar-45-miljarder-ar-gammalt"

I what to get the value of [0] if I know [1]

I know I kan get the value of [0] if I know the index of the first array like this

var theLine = newlines[2];
console.log(theLine[0]); //Vårt solsystem är 4,5 miljarder år gammalt.

But how do I get "Vårt solsystem är 4,5 miljarder år gammalt." if I know "vart-solsystem-ar-45-miljarder-ar-gammalt".

The first dimension has about 500 records, the second dimension always has two records.

Dacre Denny · Accepted Answer · 2019-08-05 00:37:35Z

If I understand correctly, you want to extract a "display" value from the first nested array, where the second item of that nested matches a value you're searching for.

There are a number of ways to achieve that - for ~500 records, the following approach based on filter() and map() should be suitable:

const data = [
  ["Vårt solsystem är 4,5 miljarder år gammalt.", "vart-solsystem-ar-45-miljarder-ar-gammalt"],
  ["Foo bar", "foo-bar"],
  ["Cat video", "cat-video"]
];

function findByValue(value) {

  /* Extract first value of result to variable "result" (if any found) */
  const [result] = data
  /* Isolate sub arrays where second entry matches search value */
  .filter(item => item[1] === value) 
  /* Map first entry of filtered array sub array items */
  .map(item => item[0])

  return result;
}

console.log(findByValue("vart-solsystem-ar-45-miljarder-ar-gammalt"), "===", "Vårt solsystem är 4,5 miljarder år gammalt.");
console.log(findByValue("foo-bar"), "===", "Foo bar");
console.log(findByValue("cat-video"), "===", "Cat video");
console.log(findByValue("no-entry"), "===", undefined);

charlietfl · Accepted Answer · 2019-08-05 00:55:14Z

0

Assuming you are dealing with unique values and only looking for a single return value you can use a combination of Array#find() and Array#some() or Array#includes() or just check value equality of second element

const data = [
  [1, 2],
  [3, 4],
  [5, 6]
];

const known = 4;
console.log(data.find(arr => arr.some(val => val === known))[0])// expect 3

edited Aug 5, 2019 at 0:55

answered Aug 5, 2019 at 0:41

charlietfl

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