CODEWITHSUNDEEP
javascript
David Carrick Sutherland
David Carrick Sutherland

Reputation: 145

Unable to extract object values in Typescript

I have been trying to convert a JavaScript web form to Typescript, and have been unable to work out how to deal with the following (which works in JavaScript):

let fieldValues = JSON.parse(cookieData);

let keys = Object.keys(fieldValues);

let values = Object.values(fieldValues);

Visual Studio tells me:

Error TS2339 Property 'values' does not exist on type 'ObjectConstructor'.

What can I do?

Upvotes: 9

Views: 55685

Answers (6)

Mingwei Samuel
Mingwei Samuel

Reputation: 3262

If you're googling this and want to know how to do this for types, you can use the (typeof x)[keyof typeof x] pattern:

const VARIANTS_BY_ID = {
  100: 'diagonal',
  120: 'knight',
  125: 'king',
  200: 'disjointGroups',
  300: 'consecutive',
} as const;

// type Variants = "diagonal" | "knight" | "king" | "disjointGroups" | "consecutive"
type Variants = (typeof VARIANTS_BY_ID)[keyof typeof VARIANTS_BY_ID];

Upvotes: 3

Walter
Walter

Reputation: 1

Well, any respose worked in my setup, so i tryed this:

 let formattedData = {}
 for (let index = 0; index < values.length; index++) {
   eval("formattedData[indexToChar(index)] = values[index]");
 }

basicaly it works because js understand it, but ts dont, so if i use eval ts dont try to parse and dont throw error, so js read it and excecute correctely. eval doc:

https://developer.mozilla.org/pt-BR/docs/Web/JavaScript/Reference/Global_Objects/eval

Upvotes: 0

Devashree
Devashree

Reputation: 221

If you need the value of a specific key you can access it using the following method :

Object(nameofobj)["nameofthekey"]

Upvotes: 20

stefku
stefku

Reputation: 117

Just as an alternative. You also could use Object.getOwnPropertyNames()

let obj = {...};
Object.getOwnPropertyNames(obj).forEach(key => {
    let value = obj[key];
});

Upvotes: 4

gyre
gyre

Reputation: 16779

If Object.values is not supported (which today is often the case), you can just map over your keys:

let cookieData = '{"key":"value"}'

let fieldValues = JSON.parse(cookieData)

let keys = Object.keys(fieldValues)

let values = keys.map(k => fieldValues[k])

console.log(keys) //=> ['key']
console.log(values) //=> ['value']

Upvotes: 9

Diullei
Diullei

Reputation: 12414

The Object.values(..) is not stabilized, so it is unsupported in many browsers (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/values)

Use map instead:

let values = Object.keys(fieldValues).map(key => fieldValues[key]);

If you really want to use this function you need to add the "es2017.object" lib on your tsconfig.json. Make sure you are using a polyfill or if your final platform support this feature.

Upvotes: 17

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