TypeScript/JavaScript array value push

Question

I have this objet : keyValue : { key : string , value : number}[];

I want to add a new element to this array from two values, like this :

 let tmpTabKV : { key : string , value : number}[];
 [...]
 tmpTabKV.push({projet.libelle, statKV.value});
 [...]
 keyValue  = tmpTabKV;

I tried multiple syntaxes and seen this : How can I add a key/value pair to a JavaScript object?

But I don't see any key to create a new object. The usage of an Array makes me an error

tmpTabKV.push(Array(projet.libelle, statKV.value));

Jamiec · Accepted Answer · 2017-02-20 15:02:17Z

6

You should be pushing an object literal to your array

let tmpTabKV : { key : string , value : number}[] = []
tmpTabKV.push({key:projet.libelle, value:statKV.value});

edited Feb 20, 2017 at 15:02

answered Feb 20, 2017 at 14:58

Jamiec

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2 Comments

AJ Richardson Over a year ago

You also need to initialize the array: let tmpTabKV : { key : string , value : number}[] = [];

Jamiec Over a year ago

@AJRichardson Thanks.

Steeve Pitis · Accepted Answer · 2017-02-20 14:59:04Z

1

According to let tmpTabKV : { key : string , value : number}[]; just do :

tmpTabKV.push({key: project.libelle, value: statKV.value})

but I think you want this :

tmpTabKV.push({[project.libelle]: statKV.value})

answered Feb 20, 2017 at 14:59

Steeve Pitis

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6 Comments

AJ Richardson Over a year ago

No, that doesn't match his interface of { key : string , value : number}

Jamiec Over a year ago

Can you actually use an array literal as the key in an object?

Steeve Pitis Over a year ago

I know, but I think this is what he want, and his interface is wrong. That's why I say 'according to his interface' first.

T.J. Crowder Over a year ago

@Jamiec: It's not an array literal, it's a computed property name. And yes, as of ES2015 (aka "ES6"), you can. It will take the value of project.libelle and use that as the property name. E.g.: let x = "answer"; let o = {[x]: 42}; console.log(o.answer); // 42

AJ Richardson Over a year ago

@SteevePitis ah, that's a good point. In that case he should change his interface to let tmpTabKV : { [key : string]: number} = {};

|

Nick · Accepted Answer · 2017-02-20 15:30:43Z

1

A few problems I've noticed: first, you're pushing a new object to the array as if it was itself an array. That is, you're relying on position of the values to map to the position of the keys. In an object, the keys are always unordered and therefore must always be specified.

tmpTabKV.push({key: project.libelle, value: statKV.value})

What you're doing with {project.libelle, startKV.value} is making an object with shorthand syntax, which would not work in your example.

In typescript, if you want to restrict the keys in an object, implement an interface.

interface KeyValue { key: string, value: number }

let tmpTabKV: KeyValue[];

// ...

tmpTabKV.push({key: project.libelle, value: number});

edited Feb 20, 2017 at 15:30

answered Feb 20, 2017 at 15:09

Nick

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Comments

Juergen Gutsch · Accepted Answer · 2017-02-20 15:01:25Z

-1

you should push a new object:

interface KeyValuePair{
   key: string:
   value: number;
}

let tmpTabKV: KeyValuePair[];

tmpTabKV.push(new {key: projet.libelle, value: statKV.value});

answered Feb 20, 2017 at 15:01

Juergen Gutsch

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2 Comments

AJ Richardson Over a year ago

You don't need the new keyword

T.J. Crowder Over a year ago

^^ "don't need" => "can't have there" :-)

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