1) Merging two or more arrays
Let's now see how we can use the concat method to merge two given arrays, array 1 and array 2
const array1 = [1,2,3,4]; const array2 = [5,6,7]; // merge array 1 into array 2 and store it in a new variable const newMergedArray = .concat(array1, array2); console.log(newMergedArray); // [1, 2, 3, 4, 5, 6, 7] console.log(array1); // [1, 2, 3, 4] console.log(array2); // [5,6,7]
const newMergedArray = .concat(array1, array2);
In the above line  creates a new array and the concat methods combine both array1, array2. This can also accept more than 2 arrays for concatenation by just adding them one next to the other
const newMergedArray = .concat(array1, array2, array 3, arrayN);
Another alternative for merging two arrays is below
const newMergedArray = array1.concat(array2, array 3, arrayN);
2) Flatten single level nested arrays
Let's assume there is a nested array as below, and we would want to flatten it in such a way that the output is [1,2,3,4,5,6,7,8], this can be achieved by using concat() method with the help of spread operator.
const array1 = [1,2,[3,4],[5,6], 7, 8]; const flattened = .concat(...array1); console.log(flattened); // [1,2,3,4,5,6,7,8]
P.S. The above code flattens just a single-level nested array.
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