Combining elements in an array with no existing values using Javascript

Question

Combining elements in an array with no existing values using Javascript

While exploring a piece of code, I started pondering over its utility.

grid.push([].concat(row));

From what I can tell, this seems identical to

grid.push([row]);

So, why the extra 'concat' operation?

javascript arrays

Answer 1

Answer №1

When you need to combine arrays without creating an array of arrays, you should use the .concat method.

var x = [1,2,3];
var y = [4];

Example 1

console.log(y.push(x));
// Result: [4, [1,2,3]]

Example 2

console.log(y.concat(x));
// Result: [4,1,2,3]

In both scenarios, the result is an array within an array. Using [].concat() ensures that the output is a single array. Whether you use [].push(row) or [].concat(row), the outcome remains the same.

To get a flattened array, remember to concatenate the array row with grid instead of pushing the concatenation result into it as shown in example 2.

Answer 2

When you need to combine arrays without creating an array of arrays, you should use the .concat method.

var x = [1,2,3];
var y = [4];

Example 1

console.log(y.push(x));
// Result: [4, [1,2,3]]

Example 2

console.log(y.concat(x));
// Result: [4,1,2,3]

In both scenarios, the result is an array within an array. Using [].concat() ensures that the output is a single array. Whether you use [].push(row) or [].concat(row), the outcome remains the same.

To get a flattened array, remember to concatenate the array row with grid instead of pushing the concatenation result into it as shown in example 2.

Answer 3

Answer №2

Take a look at my alternative solution:

const numbers = [];
const tempArray = [ 5, 10, '200$' ];
numbers.push(...tempArray);

Answer 4

Take a look at my alternative solution:

const numbers = [];
const tempArray = [ 5, 10, '200$' ];
numbers.push(...tempArray);

Answer 5

Answer №3

const emptyArray = [];
grid = [...grid, ...emptyArray, ...row];

An array can be empty as long as it follows the array format.

Answer 6

const emptyArray = [];
grid = [...grid, ...emptyArray, ...row];

An array can be empty as long as it follows the array format.

Answer 7

Answer №4

When you use grid.push([row]);, what you are actually doing is pushing an array that contains the row itself. For example, if row is an array like [0, 1, 2], then you will be pushing an array containing another array, which would look like [[0, 1, 2]].

On the other hand, with grid.push([].concat(row));, you are pushing an array that contains the elements of row directly, without creating an extra array layer.

In theory, one might wonder why not just write grid.push(row), as it seems to achieve a similar result to grid.push([].concat(row)); when row is an array.

There could be two reasons for this:

Perhaps row is not actually an array but an "array-like" object, and using [].concat(row) helps convert it into an array (similar to how Array.from works).
Or maybe the coder prefers to push a copy of row instead of the original, in order to protect it from any further modifications.

Answer 8

When you use grid.push([row]);, what you are actually doing is pushing an array that contains the row itself. For example, if row is an array like [0, 1, 2], then you will be pushing an array containing another array, which would look like [[0, 1, 2]].

On the other hand, with grid.push([].concat(row));, you are pushing an array that contains the elements of row directly, without creating an extra array layer.

In theory, one might wonder why not just write grid.push(row), as it seems to achieve a similar result to grid.push([].concat(row)); when row is an array.

There could be two reasons for this:

Perhaps row is not actually an array but an "array-like" object, and using [].concat(row) helps convert it into an array (similar to how Array.from works).
Or maybe the coder prefers to push a copy of row instead of the original, in order to protect it from any further modifications.

Combining elements in an array with no existing values using Javascript

Answer №1

Answer №2

Answer №3

Answer №4

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