
Typescript dictionary class: Learn with examples.
In this Blog Post, Learn the dictionary in typescript with examples.
Dictionary is a type of data structure with unordered list data, that contains key and value values. It is the same as map type in typescript.
How to declare and initialize a dictionary using a map?
There are multiple ways can create a dictionary.
- using map type
A map is a type introduced inES6 and typescript.
Following example contains
- the declare and create a map variable
- add the key-value pairs
- check for key exists
- get the value with a key
- delete a key and its value
- Iterate the map with keys and values
- Remove all elements from a map
- get the number of elements in a map
- retrieve all keys and values with insertion order
let employees = new Map<string, string>();
employees.set("name", "john");
// Checking for the key exist :
employees.has("name"); // true
// get a value by a key:
employees.get("name"); // john
// delete an item by a key:
employees.delete("name");
// iterate key and values
employees.forEach((item, key) => console.log(item));
// remove all from map:
employees.clear();
// size:Number of elements in Map :
console.log(employees.size)
// get All keys with insertion order
let keys = Array.from(employees.keys());
// Extract values with insertion order
let values = Array.from(employees.values());
How to declare an interface for a dictionary?
Declare an interface using indexable type in typescript
declare an interface that accepts a key as a string and value of type T
interface Dictionary<T> {
[Key: string]: T;
}
A class contains properties of the dictionary interface as below.
export class AllEmployees {
employees: Dictionary<string> = {};
}
Dictionary interfaces declare with let keyword and initialize the values, add the values.
let emps: Dictionary<string> = {};
emps["name"] = "john";
How to declare a dictionary with record type
Record is a map of key and value pairs.
A new type creates with a type alias(type keyword) and Record type.
type emps = Record<string, string>
Data initialized using object syntax as seen below.
let emps: Record<string, string> = {
{"name": "john" },
{"id": "1" }
};
Conclusion
Learned typescript dictionaries with multiple examples to declare a dictionary type in typescript