created echo example in javascript using QuickJS

echo-js/Dockerfile

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+# syntax=docker.io/docker/dockerfile:1.4
+FROM cartesi/toolchain:0.10.0 as dapp-build
+
+WORKDIR /opt/cartesi/dapp
+COPY . .

echo-js/README.md

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+# echo-js DApp
+
+echo-js is a customized DApp written in Javascript, which originally resembles the one provided by the sample [Echo Python DApp](https://github.com/cartesi/rollups-examples/tree/main/echo-python).
+
+The documentation below reflects the original application code, and should also be used as a basis for documenting any DApp created with this mechanism.
+
+## Requirements
+
+Please refer to the [rollups-examples requirements](https://github.com/cartesi/rollups-examples/tree/main/README.md#requirements).
+
+## Building
+
+To build the application, run the following command:
+
+```shell
+docker buildx bake -f docker-bake.hcl -f docker-bake.override.hcl --load
+```
+
+## Running
+
+To start the application, execute the following command:
+
+```shell
+docker compose -f ../docker-compose.yml -f ./docker-compose.override.yml up
+```
+
+The application can afterwards be shut down with the following command:
+
+```shell
+docker compose -f ../docker-compose.yml -f ./docker-compose.override.yml down -v
+```
+
+## Interacting with the application
+
+We can use the rollups-examples [frontend-console](https://github.com/cartesi/rollups-examples/tree/main/frontend-console) application to interact with the DApp.
+Ensure that the [application has already been built](https://github.com/cartesi/rollups-examples/tree/main/frontend-console/README.md#building) before using it.
+
+From within the `frontend-console` directory, you can send an input as follows:
+
+```shell
+yarn start send --input "Hello there"
+```
+
+In order to verify the notices generated by your inputs, run the command:
+
+```shell
+yarn start notices
+```
+
+The response should be something like this:
+
+```shell
+[ { epoch: '0', input: '1', notice: '0', payload: 'Hello there' } ]
+```
+
+## Deploying to a testnet
+
+Deploying the application to a blockchain requires creating a smart contract on that network, as well as running a validator node for the DApp.
+
+The first step is to build the DApp's back-end machine, which will produce a hash that serves as a unique identifier.
+
+```shell
+docker buildx bake -f docker-bake.hcl -f docker-bake.override.hcl machine --load
+```
+
+Once the machine docker image is ready, we can use it to deploy a corresponding Rollups smart contract. This requires you to define a few environment variables to specify which network you are deploying to, which account to use, and which RPC gateway to use when submitting the deploy transaction.
+
+```shell
+export NETWORK=<network>
+export MNEMONIC=<user sequence of twelve words>
+export RPC_URL=<https://your.rpc.gateway>
+```
+
+For example, to deploy to the Goerli testnet using an Alchemy RPC node, you could execute:
+
+```shell
+export NETWORK=goerli
+export MNEMONIC=<user sequence of twelve words>
+export RPC_URL=https://eth-goerli.alchemyapi.io/v2/<USER_KEY>
+```
+
+With that in place, you can submit a deploy transaction to the Cartesi DApp Factory contract on the target network by executing the following command:
+
+```shell
+DAPP_NAME=echo-js docker compose -f ./deploy-testnet.yml up
+```
+
+This will create a file at `./deployments/<network>/echo-js.address` with the deployed contract's address.
+Once the command finishes, it is advisable to stop the docker compose and remove the volumes created when executing it.
+
+```shell
+DAPP_NAME=echo-js docker compose -f ./deploy-testnet.yml down -v
+```
+
+After that, a corresponding Cartesi Validator Node must also be instantiated in order to interact with the deployed smart contract on the target network and handle the back-end logic of the DApp.
+Aside from the environment variables defined above, the node will also need a secure websocket endpoint for the RPC gateway (WSS URL) and the chain ID of the target network.
+
+For example, for Goerli and Alchemy, you would set the following additional variables:
+
+```shell
+export WSS_URL=wss://eth-goerli.alchemyapi.io/v2/<USER_KEY>
+export CHAIN_ID=5
+```
+
+Then, the node itself can be started by running a docker compose as follows:
+
+```shell
+DAPP_NAME=mydapp docker compose -f ./docker-compose-testnet.yml -f ./docker-compose.override.yml up
+```
+
+## Interacting with the deployed application
+
+With the node running, you can interact with the deployed DApp using the [frontend-console](https://github.com/cartesi/rollups-examples/tree/main/frontend-console), as described [previously](#interacting-with-the-application).
+This time, however, you need to specify the appropriate connectivity configurations.
+
+First of all, in the separate terminal for the frontend-console, define the `MNEMONIC` and `RPC_URL` variables as before:
+
+```shell
+export MNEMONIC=<user sequence of twelve words>
+export RPC_URL=<https://your.rpc.gateway>
+```
+
+Then, inputs can be sent by specifying the DApp contract's address, as follows:
+
+```shell
+yarn start send --input "Hello there" --addressFile path/to/echo-js/deployments/<network>/echo-js.address
+```
+
+Resulting notices can then be retrieved by querying the local Cartesi Node, as before:
+
+```shell
+yarn start notices
+```
+
+## Running the back-end in host mode
+
+When developing an application, it is often important to easily test and debug it. For that matter, it is possible to run the Cartesi Rollups environment in [host mode](https://github.com/cartesi/rollups-examples/tree/main/README.md#host-mode), so that the DApp's back-end can be executed directly on the host machine, allowing it to be debugged using regular development tools such as an IDE.
+
+This DApp's back-end is written in `Javascript` that using `QuickJS` engine, so to run it in your machine you need to have `QuickJS` installed.
+
+In order to start the back-end, run the following commands in a dedicated terminal:
+
+```shell
+# DIR ../echo-js/
+ROLLUP_HTTP_SERVER_URL="http://127.0.0.1:5004" qjs server/src/echo-server.js
+```
+
+The final command will effectively run the back-end and send corresponding outputs to port `5004`.
+
+After the back-end successfully starts, it should print an output like the following:
+
+```log
+HTTP rollup_server url is http://127.0.0.1:5004
+Sending finish
+```
+
+After that, you can interact with the application normally [as explained above](#interacting-with-the-application).

echo-js/config/bs-config.toml

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+[block_subscriber]
+
+# max delay between retries in seconds
+max_delay = 64
+
+# max number of retries
+max_retries = 5
+
+# timeout for block subscriber in seconds
+timeout = 120

echo-js/config/indexer-config.toml

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+[indexer_config]
+
+# unique session identifier for machine manager
+session_id = "default_rollups_id"
+
+# node starts syncing from inital epoch
+initial_epoch = 0
+
+# polling interval
+interval = 10
+
+# end points
+postgres_endpoint = "postgres://postgres:password@database/postgres"
+state_server_endpoint = "http://state_server:50051"
+mm_endpoint = "http://server_manager:5001"

echo-js/config/logic-config.toml

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+[logic_config]
+
+# unique session identifier for machine manager
+session_id = "default_rollups_id"
+
+# node starts syncing from inital epoch
+initial_epoch = 0
+
+# gas estimation/price multiplier
+gas_multiplier = 1
+gas_price_multiplier = 1
+
+# number of blocks before resubmting tx
+rate = 20
+
+# depth of blocks before considering tx finalized
+confirmations = 10
+
+# end points
+provider_http_endpoint = "http://hardhat:8545"
+ws_endpoint = "ws://hardhat:8545"
+state_fold_grpc_endpoint = "http://state_server:50051"
+mm_endpoint = "http://server_manager:5001"

echo-js/config/sf-config.toml

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+[state_fold]
+
+# concurrent events fetch for state fold access
+concurrent_events_fetch = 16
+
+# genesis block number for state fold access
+genesis_block = "0x1"
+
+# query limit error for state fold access
+query_limit_error_codes = [-32005]
+
+# number of blocks (depth) before considering state finalized
+safety_margin = 0

echo-js/config/tm-config.toml

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+[tx_manager]
+
+# max delay between retries in seconds
+max_delay = 64
+
+# max number of retries
+max_retries = 5
+
+# timeout for a sent transaction in seconds
+transaction_timeout = 5

echo-js/dapp.json

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+{
+  "fs": {
+    "files": [
+      "server",
+      "entrypoint.sh"
+    ]
+  }
+}

echo-js/deploy-testnet.yml

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+version: "3.9"
+
+services:
+  machine:
+    image: cartesi/dapp:${DAPP_NAME:?undefined DAPP_NAME}-devel-machine
+    command: xxd -c 256 -p hash; sleep 3
+    volumes:
+      - machine:/opt/cartesi/share/dapp-bin
+
+  deployer:
+    image: cartesi/rollups-cli:0.3.0
+    depends_on:
+      machine:
+        condition: service_started
+    command:
+      [
+        "create",
+        "--rpc",
+        "${RPC_URL:?undefined RPC_URL}",
+        "--mnemonic",
+        "${MNEMONIC:?undefined MNEMONIC}",
+        "--templateHashFile",
+        "/opt/cartesi/share/dapp-bin/hash",
+        "--outputFile",
+        "/deployments/${NETWORK:?undefined NETWORK}/${DAPP_NAME:?undefined DAPP_NAME}.address",
+      ]
+    volumes:
+      - machine:/opt/cartesi/share/dapp-bin:ro
+      - ./deployments:/deployments
+
+volumes:
+  machine: {}

echo-js/deployments/localhost/.chainId

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+31337