In TypeScript, there are several ways to merge arrays. In this post, we'll take a look at three of the most common methods for merging arrays in TypeScript:

• Spread operator [...array]

• Concat array.concat

• Push array.push

First, let's take a look at using the spread operator to merge arrays. This is the simplest method, and it works by spreading the elements of one array into another array. Here's an example:

let array1 = [1, 2, 3];
let array2 = [4, 5, 6];

let mergedArray = [...array1, ...array2];

console.log(mergedArray); // [1, 2, 3, 4, 5, 6]

In this example, we have two arrays, array1, and array2, and we use the spread operator (...) to spread the elements of each array into a new array, mergedArray. As you can see, the elements of both arrays are now combined in the mergedArray, in the order that they were spread in.

Another way of merging arrays is using the array.concat method, this is a very similar approach to the previous one but it's not using the spread operator, this is the way it works:

let array1 = [1, 2, 3];
let array2 = [4, 5, 6];

let mergedArray = array1.concat(array2);

console.log(mergedArray); // [1, 2, 3, 4, 5, 6]

This method is a little more explicit than concatenating the arrays, it works by calling the concat method on the first array, passing in the second array as an argument. This concatenates the two arrays, effectively merging them together into a new array.

Finally, we have the array.push method, this method works in a very similar way that array.concat but is more useful when you want to push the elements of one array into another array, this method is useful when we are working with an array that is going to change through time and we want to use the push method to push the elements of one array into another one.

let array1 = [1, 2, 3];
let array2 = [4, 5, 6];

let mergedArray = array1;

array1.push(...array2);

console.log(mergedArray); // [1, 2, 3, 4, 5, 6]

It works by calling the push method on the first array and spreading the elements of the second array into it. This pushes the elements of the second array into the first array, effectively merging them together.

In summary, these are three methods for merging arrays in TypeScript: using the spread operator, using the array.concat method, and using the array.push method. Each method has its own use case, depending on the situation, you can choose the one that works better for you.