Added MSET command

MSET command added. Requires all keys to have the same JSON Path, which might fit most use cases, but is a limitation.  Optionally we could make the path an array as well to support all use cases.

packages/json/lib/commands/MSET.spec.ts

@@ -0,0 +1,19 @@
+import { strict as assert } from 'assert';
+import testUtils, { GLOBAL } from '../test-utils';
+import { transformArguments } from './MSET';
+
+describe('MSET', () => {
+    it('transformArguments', () => {
+        assert.deepEqual(
+            transformArguments(['1', '2'], '$', [{ a: 1 }, { b: 2 }]),
+            ['JSON.MSET', '1', '$', '{ "a":"1" } ', '2', '$', '{ "b":"2"} ']
+        );
+    });
+
+    testUtils.testWithClient('client.json.mGet', async client => {
+        assert.deepEqual(
+            await client.json.mGet(["1", "2"], "$", [{ a: 1 }, { b: 2 }]),
+          [null, null]
+        );
+    }, GLOBAL.SERVERS.OPEN);
+});

packages/json/lib/commands/MSET.ts

@@ -0,0 +1,24 @@
+import { RedisJSON, transformRedisJsonArgument } from ".";
+
+export const FIRST_KEY_INDEX = 1;
+
+export function transformArguments(
+    keys: Array<string>,
+    path: string,
+    json: Array<RedisJSON>
+): Array<string> {
+    
+    if (keys.length != json.length)
+        throw new Error("Number of keys and json objects must be equal");
+
+    let args: Array<string> = ["JSON.SET"];
+
+    // walk through the key array, adding the key, the path and the json objects, calling transformRedisJsonArgument for each
+    for (let i = 0; i < keys.length; i++) {
+        args.push(keys[i], path, transformRedisJsonArgument(json[i]));
+    }
+
+    return args;
+}
+
+export declare function transformReply(): "OK" | null;