Add declaration file to support TypeScript better

package.json

@@ -21,6 +21,7 @@
     "url": "https://github.com/makerdao/multicall.js.git"
   },
   "main": "dist/multicall.cjs.js",
+  "types": "types/multicall.d.ts",
   "module": "dist/multicall.esm.js",
   "unpkg": "dist/multicall.umd.js",
   "files": [

types/multicall.d.ts

@@ -0,0 +1,116 @@
+/// <reference types="node"/>
+
+declare module '@makerdao/multicall' {
+  import { BigNumber } from 'bignumber.js';
+
+  export interface IConfig {
+    preset: 'mainnet' | 'kovan' | 'rinkeby' | 'goerli' | 'xdai' | 'ropsten';
+    rpcUrl: string;
+    multicallAddress: string;
+    interval: number;
+    staleBlockRetryWait: number;
+    errorRetryWait: number;
+  }
+
+  export interface IPostProcess {
+    (v: any): any;
+  }
+
+  export interface ICall {
+    target: string;
+    call: string[];
+    returns: (string | IPostProcess)[][];
+  }
+
+  export interface IArgumentsMapping {
+    [key: string]: string[];
+  }
+
+  export interface IKeysValues {
+    [key: string]: any;
+  }
+
+  export interface IResult {
+    blockNumber: BigNumber;
+    original: IKeysValues;
+    transformed: IKeysValues;
+    keyToArgMap: IArgumentsMapping;
+  }
+
+  export interface IResponse {
+    results: IResult;
+  }
+
+  export interface IUpdate {
+    type: string;
+    value: any;
+    args: any[];
+  }
+
+  export interface ISubscription {
+    unsub(): void;
+  }
+
+  export interface ISubscriber {
+    subscribe(callback: (updates: IUpdate[]) => void): ISubscription;
+  }
+
+  export interface IPollData {
+    id: number;
+    latestBlockNumber: number;
+    retry?: number;
+  }
+
+  export interface IState {
+    model: Partial<ICall>[];
+    store: IKeysValues;
+    storeTransformed: IKeysValues;
+    keyToArgMap: IKeysValues;
+    latestPromiseId: number;
+    latestBlockNumber: number | null;
+    id: number;
+    listeners: {
+      subscribe: any[];
+      block: any[];
+      poll: any[];
+      error: any[];
+    };
+    handler: any | null;
+    wsReconnectHandler: any | null;
+    watching: boolean;
+    config: Partial<IConfig>;
+    ws: WebSocket | null;
+  }
+
+  export interface IWatcher {
+    initialFetch: Promise;
+
+    schemas: Partial<ICall>[];
+
+    tap(callback: (calls: Partial<ICall>[]) => Partial<ICall>[]): Promise<undefined>;
+
+    poll(): Promise<void>;
+
+    subscribe(callback: (update: IUpdate) => void): ISubscriber;
+
+    batch(): ISubscriber;
+
+    onNewBlock(callback: (blockNumber: number) => void): ISubscription;
+
+    onPoll(callback: (pollData: IPollData) => void): ISubscription;
+
+    onError(callback: (error: Error, state: IState) => void): ISubscription;
+
+    recreate(calls: Partial<ICall>[], config: Partial<IConfig>): Promise<undefined>;
+
+    start(): Promise<undefined>;
+
+    stop(): undefined;
+
+    awaitInitialFetch(): Promise<undefined>;
+  }
+
+  export function aggregate(calls: Partial<ICall>[], config: Partial<IConfig>): Promise<IResponse>;
+
+  export function createWatcher(calls: Partial<ICall>[], config: Partial<IConfig>): IWatcher;
+}