Externalize strings and use a formatter to substitute variables into string

Question

I'd like to externalize some strings but still use some form of string substitution.

In some of my node based projects I've used:

var format = require('string-format');

format(Constants.COUNTRY_WEATHER_ENDPOINT, {
  country: country
})

However In Typescript, I've been trying something like this ..

Error:

Cannot find name 'country'.at line 18 col 66 in repo/src/app/constants.ts

Constants.ts

export class Constants {
  public static COUNTRY_WEATHER_ENDPOINT = `/api/country/${country}/weather`;
}

TestService.ts

import { Constants } from './constants';

export class TestService {
  constructor(private $http) { }

  public getWeather(country) {
    let url = Constants.COUNTRY_WEATHER_ENDPOINT;
    return this.$http.get(
      url,
      .then(response => response);
  }
}

TestService.$inject = ['$http'];

Answer 1

Use arrow functions:

export const Constants: { readonly [name: string]: (key: string) => string } = {
  countryWeatherEndpoint: country => `/api/country/${country}/weather`
}

Then do:

import { Constants } from "./constants";
// ...
const url = Constants.countryWeatherEndpoint(country);
// use your url