Best approach in extracting the values of array inside object in js

Question

What is best approach in extracting the below object. I tried two ways. Can this be refactored in any other way to optimize the performance?

const data = {
    "postcode": [
        "123456"
    ],
    "time": [
        "05:11"
    ]
};

Approach 1:

for (const element of Object.entries(data)) {
    const key = element[0];
    const value = element[1][0];
    data[key] = value;
}

Approach 2:

for (const key in data) {
    if (Object.hasOwnProperty.call(data, key)) {
        data[key] = data[key][0];
    }
}

console.log('data ', data);

What do you mean 'extract the below object'? Are there constraints on what the object's contents will be (i.e. only one element in the array)? What's the expected output? — Jack Bashford
– Jack Bashford, Commented Jun 10, 2022 at 6:30
Performance of your code looks pretty good as is. You can use in-built methods like Object.fromEntries() and .map() to make your code more concise, but if you're after performance improvements I don't think much can be done, other than some potential micro-optimizations that won't make much of a difference in the grand scheme of things. — Nick Parsons
– Nick Parsons, Commented Jun 10, 2022 at 6:32
@NickParsons Can you post an example with map and fromEntries? — kittu
– kittu, Commented Jun 10, 2022 at 6:33
@kittu it would be something like this const res = Object.fromEntries(Object.entries(data).map(([key, [val]]) => [key, val]));, adding this as a comment as this doesn't answer your question of optimizing your code (it would make your code slightly slower actually), it's just more concise I guess — Nick Parsons
– Nick Parsons, Commented Jun 10, 2022 at 6:36
@mousetail In your answer you've refactored OPs first code-block, which I think does answer the refactoring part of the question, and your example doesn't really lower the performance of the existing code, so I think your answer is fine :). I do think OPs second approach of for (const key in data) { would be the most efficient (assuming the prototype isn't filled with enumerable properties), as it is only one iteration of the object, whereas .entries() + for..of leads to two iterations over the keys/values. — Nick Parsons
– Nick Parsons, Commented Jun 10, 2022 at 6:55

mousetail · Accepted Answer · 2022-06-10 06:54:18Z

3

A concise method is this:

for (const [key, [value]] of Object.entries(data)) {
    data[key] = value
}

Notice the extra set of [] around [value] to extract the value from that array immediately too.

Of course, conciseness isn't always better and you may prefer your other solutions if you think they are more readable.

In terms of performance this isn't any better than your first solution. Your second option will be more memory efficient though it heavily depends on the size and shape of your object.

edited Jun 10, 2022 at 6:54

answered Jun 10, 2022 at 6:34

mousetail

8,1696 gold badges31 silver badges53 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

TheRakeshPurohit · Accepted Answer · 2022-06-10 06:33:57Z

0

This approach will solve your problem. MDN recommended!

const object1 = {
  a: 'somestring',
  b: 42
};

for (const [key, value] of Object.entries(object1)) {
  console.log(`${key}: ${value}`);
}

// expected output:
// "a: somestring"
// "b: 42"

answered Jun 10, 2022 at 6:33

TheRakeshPurohit

5491 gold badge6 silver badges22 bronze badges

Collectives™ on Stack Overflow

Best approach in extracting the values of array inside object in js

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related