JavaScript 2D arrays and returning matching rows

Question

I have 2 arrays, each is like a database table row set.

array1 = [ ['AB2C', 'Red', 113], ['BE4F', 'Green', 164], ['AE3G', 'Blue', 143], ] array2 = [ [143, 'FabricB2', 'W5'], [189, 'FabricC9', 'W4'], [113, 'FabricA3', ' W5'], [143, 'FabricD1', 'W6']];

I want to do a join and find matching rows, returning the matched rows in array2 along with the matched row in array1. The returned matching array should look like this:

[143, 'FabricB2', 'W5', 'AE3G', 'Blue', 143], [113, 'FabricA3', ' W5', 'AB2C', 'Red', 113], [143, 'FabricD1', 'W6', 'AE3G', 'Blue', 143]

I tried to use JavaScript methods map(), filter(), flatMap(), spread operator but can't get the result. Anyone can help me with this? With the shortest code? The one I have below does not work.

function testArrayFunction() { array1 = [ ['AB2C', 'Red', 113], ['BE4F', 'Green', 164], ['AE3G', 'Blue', 143], ]; array2 = [ [143, 'FabricB2', 'W5'], [189, 'FabricC9', 'W4'], [113, 'FabricA3', ' W5'], [143, 'FabricD1', 'W6']]; var array1Element = 2; var array2Element = 0; var res = array1 .map(x => [ ... array2 .filter( y => y[array2Element] === x[array1Element ] ) ,...x ] ); console.log(res); }

Does not give the expected result which is this

[143, 'FabricB2', 'W5', 'AE3G', 'Blue', 143], [113, 'FabricA3', ' W5', 'AB2C', 'Red', 113], [143, 'FabricD1', 'W6', 'AE3G', 'Blue', 143]

Gives this which is not what I want

Info [ [ [ 113, 'FabricA3', ' W5' ], 'AB2C', 'Red', 113 ], [ 'BE4F', 'Green', 164 ], [ [ 143, 'FabricB2', 'W5' ], [ 143, 'FabricD1', 'W6' ], 'AE3G', 'Blue', 143 ] ]

Aman Thakur · Accepted Answer · 2024-10-11 11:12:46Z

//You can try this : const resultArr = array1.flatMap(x => array2 .filter(y=>y[0] === x[2]) .map(y => [...y,...x]) );

Konrad · Accepted Answer · 2024-10-11 11:13:37Z

It's easier to use reduce

const array1 = [ ['AB2C', 'Red', 113], ['BE4F', 'Green', 164], ['AE3G', 'Blue', 143], ] const array2 = [ [143, 'FabricB2', 'W5'], [189, 'FabricC9', 'W4'], [113, 'FabricA3', ' W5'], [143, 'FabricD1', 'W6'] ]; const result = array2.reduce((result, current) => { const other = array1.find(b => current[0] === b[2]) if (other) { result.push([...current, ...other]) } return result }, []) console.log(result)

Nina Scholz · Accepted Answer · 2024-10-11 11:26:37Z

You could take a reference to the items of array1 and return items of array2 only if a reference to array1 exists.

const array1 = [['AB2C', 'Red', 113], ['BE4F', 'Green', 164], ['AE3G', 'Blue', 143]], array2 = [[143, 'FabricB2', 'W5'], [189, 'FabricC9', 'W4'], [113, 'FabricA3', ' W5'], [143, 'FabricD1', 'W6']], references = Object.fromEntries(array1.map(a => [a[2], a])), result = array2.reduce((r, a) => { if (references[a[0]]) r.push([...a, ...references[a[0]]]) return r; }, []); console.log(result);

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