Filtering a nested array on a single index based on multiple possible values

Question

Lets say I have a nested array:

var test_array = [
 ["0", "0.1", "4.2", "Kramer Street"],
 ["1", "0.2", "3.5", "Lamar Avenue"],
 ["3", "4.2", "7.1", "Kramer Street"]
];

I also have a small array of string values. This is a simplified example as there could be a single value or multiple values:

var string_values = ["0.1", 4.2"]

I want to filter or parse the array to just get the subarrays where index 1 and only index 1 is equal to either of my string_values. I've tried the following approach but its cumbersome (although it works). Is there a better way using .filter or .find (or another single line method) to achieve this?

var test_array = [
     ["0", "0.1", "4.2", "Kramer Street"],
     ["1", "0.2", "3.5", "Lamar Avenue"],
     ["3", "4.2", "7.1", "Kramer Street"]
    ];

var string_values = ["0.1", "4.2"]
var new_array = [];

for (let i=0; i < test_array.length; i++) { 
    if (string_values.indexOf(test_array[i][1]) !== -1) { 
        new_array.push(test_array[i]); 
    } 
}

console.log(new_array);

Ben Stephens · Accepted Answer · 2021-05-18 20:29:27Z

1

Maybe something like:

const test_array = [
  ["0", "0.1", "4.2", "Kramer Street"],
  ["1", "0.2", "3.5", "Lamar Avenue"],
  ["3", "4.2", "7.1", "Kramer Street"]
];

const string_values = ["0.1", "4.2"];

const res = test_array.filter(([_, v]) => string_values.includes(v));

console.log(JSON.stringify(res));

In case string_values could get significantly larger it might be worth using Set (MDN, blog post on performance) :

const test_array = [
  ["0", "0.1", "4.2", "Kramer Street"],
  ["1", "0.2", "3.5", "Lamar Avenue"],
  ["3", "4.2", "7.1", "Kramer Street"]
];

const string_values = new Set(["0.1", "4.2"]);

const res = test_array.filter(({ 1: v }) => string_values.has(v));

console.log(JSON.stringify(res));

(The way I got v differently in the second example is irrelevant to the use of Set, I just find myself suddenly remembering that you can destructure arrays like that occasionally.)

edited May 18, 2021 at 20:29

answered May 18, 2021 at 20:11

Ben Stephens

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1 Comment

gwydion93 Over a year ago

Wow, both of these solutions are great, but I chose this one because of the application of Set() which might help in the more complex situations. My example is a very simplified illustration of the actual arrays.

Dharman · Accepted Answer · 2021-05-18 20:21:55Z

1

var test_array = [
     ["0", "0.1", "4.2", "Kramer Street"],
     ["1", "0.2", "3.5", "Lamar Avenue"],
     ["3", "4.2", "7.1", "Kramer Street"]
    ];

var string_values = ["0.1", "4.2"]
var new_array = test_array.filter(obj=> string_values.find(num=> num === obj[1]))

console.log(new_array)

edited May 18, 2021 at 20:21

Dharman♦

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answered May 18, 2021 at 20:16

Sunny

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