How to parse JSON string in Typescript

Question

Is there a way to parse strings as JSON in Typescript.
Example: In JS, we can use JSON.parse(). Is there a similar function in Typescript?

I have a

Answer 1

JSON.parse is available in TypeScript, so you can just use it :

JSON.parse('{"name": "Bob", "error": false}') // Returns a value of type 'any'

However, you will often want to parse a JSON object while making sure it matches a certain type, rather than dealing with a value of type any. In that case, you can define a function such as the following :

function parse_json(
  json: string,
  type_definitions: { [Key in keyof TargetType]: (raw_value: any) => TargetType[Key] }
): TargetType {
  const raw = JSON.parse(json); 
  const result: any = {};
  for (const key in type_definitions) result[key] = type_definitions[key](raw[key]);
  return result;
}

This function takes a JSON string and an object containing individual functions that load each field of the object you are creating. You can use it like so:

const value = parse_json(
  '{"name": "Bob", "error": false}',
  { name: String, error: Boolean, }
);