How to get an object by the name in Javascript?

Question

I have a ridiculous object like this.

{
order: ["a1","a2","a3","a4"],  
posts: {
a1: {id: "a1",message: "This is a1"},
a4: {id: "a4",message: "This is a4"},
a3: {id: "a3",message: "This is a3"},
a2: {id: "a2",message: "This is a2"},
}
}

I need to get "message" value from "posts" object with the order that define in "order" array. I can foreach the "order" array, but how to know when I have "a1" string, I need to take "a1" object in "posts" object?

Thank you!

const str = 'a1'; obj.posts[str] ??? It's not clear what you're asking — CertainPerformance
– CertainPerformance, Commented Sep 30, 2018 at 7:58

Shubham Khatri · Accepted Answer · 2018-09-30 07:59:02Z

7

All you have to do is map over the order array and return the object based on keys using brackets notation like

const data = {
order: ["a1","a2","a3","a4"],  
posts: {
a1: {id: "a1",message: "This is a1"},
a4: {id: "a4",message: "This is a4"},
a3: {id: "a3",message: "This is a3"},
a2: {id: "a2",message: "This is a2"},
}
}

const res = data.order.map((id) => {
    return data.posts[id];
})

console.log(res);

answered Sep 30, 2018 at 7:59

Shubham Khatri

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rony2k6 · Accepted Answer · 2018-09-30 08:12:46Z

0

Hope below code may help.

const data = {
order: ["a1","a2","a3","a4"],  
posts: {
a1: {id: "a1",message: "This is a1"},
a4: {id: "a4",message: "This is a4"},
a3: {id: "a3",message: "This is a3"},
a2: {id: "a2",message: "This is a2"},
}
}

Object.entries(data.order).forEach(([key, val]) => {
    console.log(data.posts[val]);          
});

answered Sep 30, 2018 at 8:12

rony2k6

755 bronze badges

4 Comments

t.niese Over a year ago

Why do you suggest to write Object.entries(data.order).forEach(([key, val]) => { instead of simply writing data.order.forEach( val => {? What is the reason for using Object.entries and destructing here?

rony2k6 Over a year ago

1) there was no specific reason for keeping key. 2) I used Object.entries, because it fits properly for the questioner expectation to access posts values in order by order.

Ngo Kim Huynh Over a year ago

I tried your idea with forEach order and get posts[value]. It can work too. I didn't know we can use posts[id] when posts is not an array.

t.niese Over a year ago

For 2. then you should definitily not use Object.entries() because [...]the Object.entries() method returns[...]in the same order as that provided by a for...in loop and for...in

[...]for...in should not be used to iterate over an Array [...]There is no guarantee that for...in will return the indexes in any particular order.

so the order is not guaranteed for your code.

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