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; } = {};11 Answers
To loop over the key/values, use a for in loop:
for (let key in myDictionary) { let value = myDictionary[key]; // Use `key` and `value`
}< ES 2017:
Object.keys(obj).forEach(key => { let value = obj[key];
});>= ES 2017:
Object.entries(obj).forEach( ([key, value]) => console.log(key, value)
);How about this?
for (let [key, value] of Object.entries(obj)) { ...
}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]; }
}Shortest way to get all dictionary/object values:
Object.keys(dict).map(k => dict[k]);Or this ways:
Object.entries(dict).map([k,v] => /* ... */);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 statementSo 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.
With es2019, this is now even simpler:
- We can use
ofsystematic - No longer need to wrap the dictionary with
Object.entries
Example:
let someMap: Map<number, number> = new Map()
someMap.set(3, 7);
someMap.set(4, 12);
for (let [key, value] of someMap) { console.log(key, value)
}Output:
3 7
4 12Ians 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`
}If you want to loop only through object value take a look at Object.values
To get the keys:
function GetDictionaryKeysAsArray(dict: {[key: string]: string;}): string[] { let result: string[] = []; Object.keys(dict).map((key) => result.push(key), ); return result;
}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] }));
}
