simple-json-api-client.ts

namespace JSONAPIClientUtils {
  export const queryParams = (params: { [key: string]: any }) => {
    return Object.keys(params)
      .map(k => encodeURIComponent(k) + "=" + encodeURIComponent(params[k]))
      .join("&");
  };

  const DEFAULT_HEADERS = {
    Accept: "application/json",
    "Content-Type": "application/json"
  };

  export const mergeHeaders = (
    headers: object | undefined
  ): Record<string, string> => {
    if (!headers) {
      return DEFAULT_HEADERS;
    }
    return Object.assign({}, DEFAULT_HEADERS, headers);
  };
}

enum HTTP_METHOD {
  GET = "GET",
  POST = "POST",
  PUT = "PUT",
  PATCH = "PATCH",
  DELETE = "DELETE"
}

interface JSONAPIClientInterface {
  readonly baseUrl: string;
  get<T>(endpoint: string, headers?: object, params?: object): Promise<T>;
  post<T>(endpoint: string, headers?: object, body?: object): Promise<T>;
  put<T>(endpoint: string, headers?: object, body?: object): Promise<T>;
  patch<T>(endpoint: string, headers?: object, body?: object): Promise<T>;
  delete<T>(endpoint: string, headers?: object): Promise<T>;
}

export class JSONAPIClient implements JSONAPIClientInterface {
  readonly baseUrl: string;
  constructor(baseUrl: string) {
    this.baseUrl = baseUrl;
  }

  get<T>(endpoint: string, headers?: object, params?: object): Promise<T> {
    let url = [this.baseUrl, endpoint].join("/");
    if (params) {
      url +=
        (url.indexOf("?") === -1 ? "?" : "&") +
        JSONAPIClientUtils.queryParams(params);
    }
    return fetch(url, {
      headers: JSONAPIClientUtils.mergeHeaders(headers),
      method: HTTP_METHOD.GET
    }).then(res => res.json());
  }

  post<T>(endpoint: string, headers?: object, body?: object): Promise<T> {
    let url = [this.baseUrl, endpoint].join("/");
    return fetch(url, {
      headers: JSONAPIClientUtils.mergeHeaders(headers),
      method: HTTP_METHOD.POST,
      body: JSON.stringify(body)
    }).then(res => res.json());
  }

  put<T>(endpoint: string, headers?: object, body?: object): Promise<T> {
    let url = [this.baseUrl, endpoint].join("/");
    return fetch(url, {
      headers: JSONAPIClientUtils.mergeHeaders(headers),
      method: HTTP_METHOD.PUT,
      body: JSON.stringify(body)
    }).then(res => res.json());
  }

  patch<T>(endpoint: string, headers?: object, body?: object): Promise<T> {
    let url = [this.baseUrl, endpoint].join("/");
    return fetch(url, {
      headers: JSONAPIClientUtils.mergeHeaders(headers),
      method: HTTP_METHOD.PATCH,
      body: JSON.stringify(body)
    }).then(res => res.json());
  }

  delete<T>(endpoint: string, headers?: object): Promise<T> {
    let url = [this.baseUrl, endpoint].join("/");
    return fetch(url, {
      headers: JSONAPIClientUtils.mergeHeaders(headers),
      method: HTTP_METHOD.DELETE
    }).then(res => res.json());
  }
}