Instead of returning the array itself, the `push()` method in JavaScript actually returns the length of the array

Question

Instead of returning the array itself, the `push()` method in JavaScript actually returns the length of the array

My goal is to create a fresh array by including an element in an existing array using the "push()" method.

Here is the original array:

let arr = [{label: 1, value: 1}, {label: 2, value: 2}];

This is the new element I wish to add to the existing array:

{label: 3, value: 3}

Below is the code snippet with the "push()" method implemented:

let arr = [{label: 1, value: 1}, {label: 2, value: 2}];

let newArr = arr.push({label: 3, value: 3});

console.log(newArr); // 3

However, it is worth noting that the "push()" method actually returns the length of the new array (which is "3" in this case) to the variable "newArr". My intention, on the other hand, is to obtain the updated array itself rather than just its length for the "newArr" variable. Are there any alternative methods to achieve this?

javascript arrays array-push

Answer 1

Answer №1

When using push, you are actually making changes to the original array. Immutable array extension is only supported in ES2015+ (compatible with all major browsers). To achieve this, you can utilize the spread operator ...:

const source = [1, 2];
const updated = [...source, 3];
console.log(updated); // [1, 2, 3]

It's important to note that the keyword new is reserved and cannot be used as an identifier.

Answer 2

When using push, you are actually making changes to the original array. Immutable array extension is only supported in ES2015+ (compatible with all major browsers). To achieve this, you can utilize the spread operator ...:

const source = [1, 2];
const updated = [...source, 3];
console.log(updated); // [1, 2, 3]

It's important to note that the keyword new is reserved and cannot be used as an identifier.

Answer 3

Answer №2

Initially, the new keyword serves a specific purpose in javascript and cannot be employed as a variable name.

Check out reserved keywords in javascript here.

Additionally, the push method operates in place, eliminating the need to assign it to a new variable. It alters the original array instead of generating a new one.

var array = [{label: 1, value: 1}, {label:2, value:2}];
    array.push({label:3, value:3});
    
    console.log(array);

Answer 4

Initially, the new keyword serves a specific purpose in javascript and cannot be employed as a variable name.

Check out reserved keywords in javascript here.

Additionally, the push method operates in place, eliminating the need to assign it to a new variable. It alters the original array instead of generating a new one.

var array = [{label: 1, value: 1}, {label:2, value:2}];
    array.push({label:3, value:3});
    
    console.log(array);

Answer 5

Answer №3

Hello user12345, In your explanation, you mentioned that using arr.push({label:3, value:3}) adds a new object to the array. To see this in action, simply print the array after pushing the new object.

For example:

var myArray = [{label: 1, value: 1}, {label:2, value:2}],
myArray.push({label:3, value:3}),
var newArray = myArray; 
console.log(newArray)

Answer 6

Hello user12345, In your explanation, you mentioned that using arr.push({label:3, value:3}) adds a new object to the array. To see this in action, simply print the array after pushing the new object.

For example:

var myArray = [{label: 1, value: 1}, {label:2, value:2}],
myArray.push({label:3, value:3}),
var newArray = myArray; 
console.log(newArray)

Answer 7

Answer №4

Avoid utilizing const and opt for using arr#push instead. It is sufficient to append new items to the array.

var arr= [{label: 1, value: 1}, {label:2, value:2}] 
arr.push({label:3, value:3}) 
 console.log(arr)

Answer 8

Avoid utilizing const and opt for using arr#push instead. It is sufficient to append new items to the array.

var arr= [{label: 1, value: 1}, {label:2, value:2}] 
arr.push({label:3, value:3}) 
 console.log(arr)

Answer 9

Answer №5

An excellent resource for learning JavaScript is the Mozilla Developer Network (MDN). When you visit the Array#push specification, you will discover that this method modifies the original array and provides the new length of the array as its return value.

Answer 10

An excellent resource for learning JavaScript is the Mozilla Developer Network (MDN). When you visit the Array#push specification, you will discover that this method modifies the original array and provides the new length of the array as its return value.

Answer 11

Answer №6

According to the MDN documentation, the push method returns the new length of the array, not the new array or the added value.

When you use the push function, it directly modifies the original array without the need for reassigning!

If you want the expected result, you can modify your code like this: arr.push({label:3, value:3});

And then assign it to a new array like so: const newArr = arr;

Answer 12

According to the MDN documentation, the push method returns the new length of the array, not the new array or the added value.

When you use the push function, it directly modifies the original array without the need for reassigning!

If you want the expected result, you can modify your code like this: arr.push({label:3, value:3});

And then assign it to a new array like so: const newArr = arr;

Answer 13

Answer №7

To retrieve the updated array for the variable "newArr," you can utilize the "concat()" method as shown below:

let arr = [{label: 1, value: 1}, {label: 2, value: 2}];

let newArr = arr.concat({label: 3, value: 3});

console.log(newArr); 
// [
//   {label: 1, value: 1}, 
//   {label: 2, value: 2}, 
//   {label: 3, value: 3}
// ]

In this scenario, there is no necessity for the "newArr" variable. The updated array is directly assigned to the original variable "arr":

let arr = [{label: 1, value: 1}, {label: 2, value: 2}];

arr = arr.concat({label: 3, value: 3});

console.log(arr);
// [
//   {label: 1, value: 1},
//   {label: 2, value: 2},
//   {label: 3, value: 3}
// ]

Answer 14

To retrieve the updated array for the variable "newArr," you can utilize the "concat()" method as shown below:

let arr = [{label: 1, value: 1}, {label: 2, value: 2}];

let newArr = arr.concat({label: 3, value: 3});

console.log(newArr); 
// [
//   {label: 1, value: 1}, 
//   {label: 2, value: 2}, 
//   {label: 3, value: 3}
// ]

In this scenario, there is no necessity for the "newArr" variable. The updated array is directly assigned to the original variable "arr":

let arr = [{label: 1, value: 1}, {label: 2, value: 2}];

arr = arr.concat({label: 3, value: 3});

console.log(arr);
// [
//   {label: 1, value: 1},
//   {label: 2, value: 2},
//   {label: 3, value: 3}
// ]

Instead of returning the array itself, the `push()` method in JavaScript actually returns the length of the array

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

Answer №6

Answer №7

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