TypeScript, Looping through a dictionary

Question

In my code, I have a couple of dictionaries (as suggested here) which is String indexed. Due to this being a bit of an improvised type, I was wondering if there any suggestions on how I would be able to loop through each key (or value, all I need the keys for anyway). Any help appreciated!

myDictionary: { [index: string]: any; } = {};

Answer 1

To loop over the key/values, use a for in loop:

for (let key in myDictionary) {
    let value = myDictionary[key];
    // Use `key` and `value`
}

Answer 2

< ES 2017:

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

>= ES 2017:

Object.entries(obj).forEach(
  ([key, value]) => console.log(key, value)
);

Answer 3

How about this?

for (let [key, value] of Object.entries(obj)) {
    ...
}

Answer 4

There is one caveat to the key/value loop that Ian mentioned. If it is possible that the Objects may have attributes attached to their Prototype, and when you use the in operator, these attributes will be included. So you will want to make sure that the key is an attribute of your instance, and not of the prototype. Older IEs are known for having indexof(v) show up as a key.

for (const key in myDictionary) {
    if (myDictionary.hasOwnProperty(key)) {
        let value = myDictionary[key];
    }
}

Answer 5

Shortest way to get all dictionary/object values:

Object.keys(dict).map(k => dict[k]);

Or this ways:

Object.entries(dict).map([k,v] => /* ... */);

Answer 6

Ians Answer is good, but you should use const instead of let for the key because it never gets updated.

for (const key in myDictionary) {
    let value = myDictionary[key];
    // Use `key` and `value`
}

Answer 7

If you just for in a object without if statement hasOwnProperty then you will get error from linter like:

for (const key in myobj) {
   console.log(key);
}

WARNING in component.ts
for (... in ...) statements must be filtered with an if statement

So the solutions is use Object.keys and of instead.

for (const key of Object.keys(myobj)) {
   console.log(key);
}

Hope this helper some one using a linter.

Answer 8

To get the keys:

function GetDictionaryKeysAsArray(dict: {[key: string]: string;}): string[] {
  let result: string[] = [];
  Object.keys(dict).map((key) =>
    result.push(key),
  );
  return result;
}

Answer 9

this is my function, i hope this help

function recordToArray<TypeOfSchema>(
  data: Record<string, TypeOfSchema>
): Array<TypeOfSchema> {
  return Object.keys(data).map((key: string) => ({ id: key, ...data[key] }));
}