Upgrade deps and convert to TypeScript

.eslintignore

@@ -1,2 +1,4 @@
 node_modules
-src/parser.js
+package.json
+src/parser.ts
+dist

.eslintrc

@@ -1,4 +1,5 @@
 ---
+# set:ft=yaml:
 
 env:
   browser: true
@@ -7,17 +8,24 @@ env:
   node: true
 
 plugins:
+  - "@typescript-eslint"
   - jest
   - prettier
 
 extends:
   - eslint:recommended
   - plugin:jest/recommended
   - plugin:prettier/recommended
+  - plugin:@typescript-eslint/recommended
+
+parser: "@typescript-eslint/parser"
 
 parserOptions:
   ecmaVersion: 2018
 
+ignorePatterns:
+  - "src/parser.ts"
+
 rules:
   indent:
   - error
@@ -47,3 +55,5 @@ rules:
 
   prettier/prettier:
   - error
+
+  "@typescript-eslint/ban-ts-comment": 'off'

.github/workflows/node.js.yml

@@ -16,18 +16,14 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [10.x, 12.x, 14.x, 15.x]
+        node-version: [16.x, 17.x]
         # See supported Node.js release schedule at https://nodejs.org/en/about/releases/
 
     steps:
-    - uses: actions/checkout@v2 
+    - uses: actions/checkout@v2
     - name: Use Node.js ${{ matrix.node-version }}
       uses: actions/setup-node@v1
       with:
         node-version: ${{ matrix.node-version }}
-    - uses: borales/actions-yarn@v2.0.0
-      with:
-        cmd: install
-    - uses: borales/actions-yarn@v2.0.0
-      with:
-        cmd: test
+    - run: yarn
+    - run: yarn test

.gitignore

@@ -1 +1,4 @@
 node_modules
+src/parser.ts
+dist
+.eslintcache

README.md

@@ -12,7 +12,7 @@ a user.
 
 ## How does it work?
 
-It uses a [PegJS](https://pegjs.org/) grammar to transform JQ expressions
+It uses a [parsed expression grammar][peg] (via [Peggy][peggy]) to transform JQ expressions
 into a series of "op codes", with each one representing a JQ filter
 operation. Each op code is executed with a context, which is initialised
 with the input object. As each op code executes, the context is updated.
@@ -26,3 +26,6 @@ with the input object. As each op code executes, the context is updated.
 
    * Complete implementation of JQ (but the level of completeness may
      increase over time).
+
+[peg]: https://en.wikipedia.org/wiki/Parsing_expression_grammar
+[peggy]: https://peggyjs.org/

package.json

@@ -2,21 +2,39 @@
   "name": "@elastic/micro-jq",
   "version": "1.4.3",
   "description": "Small implementation of jq",
-  "main": "./src/index.js",
+  "main": "./dist/index.js",
   "license": "Apache-2.0",
-  "bin": "./src/cli.js",
+  "bin": "./dist/cli.js",
+  "types": "./dist/index.d.ts",
   "scripts": {
-    "build": "pegjs -o ./src/parser.js ./src/parser.pegjs",
-    "lint": "eslint .",
+    "build": "peggy --plugin ./node_modules/ts-pegjs --cache -o ./src/parser.ts ./src/parser.pegjs && tsc --declaration --outdir dist src/*.ts",
+    "lint": "eslint --cache src",
     "test": "yarn lint && yarn build && jest"
   },
   "devDependencies": {
-    "eslint": "^7.31.0",
+    "@types/jest": "^27.4.0",
+    "@typescript-eslint/eslint-plugin": "^5.12.0",
+    "@typescript-eslint/parser": "^5.12.0",
+    "eslint": "^8.9.0",
     "eslint-config-prettier": "^8.3.0",
-    "eslint-plugin-jest": "^24.4.0",
-    "eslint-plugin-prettier": "^3.4.0",
-    "jest": "^27.0.6",
-    "pegjs": "^0.10.0",
-    "prettier": "^2.3.2"
+    "eslint-plugin-jest": "^26.1.0",
+    "eslint-plugin-prettier": "^4.0.0",
+    "jest": "^27.5.1",
+    "peggy": "^1.2.0",
+    "prettier": "^2.5.1",
+    "ts-jest": "^27.1.3",
+    "ts-pegjs": "^1.2.1",
+    "typescript": "^4.5.5"
+  },
+  "jest": {
+    "preset": "ts-jest",
+    "testEnvironment": "node",
+    "globals": {
+      "ts-jest": {
+        "tsconfig": {
+          "noImplicitAny": false
+        }
+      }
+    }
   }
 }

src/cli.js → src/cli.ts

@@ -1,11 +1,11 @@
 /* eslint-disable no-console */
 
-const fs = require('fs')
-const executeScript = require('./execute')
+import { readFileSync } from 'fs'
+import executeScript from './execute'
 
 const script = process.argv[2] || '.'
 
-const input = JSON.parse(fs.readFileSync(0, 'utf8'))
+const input = JSON.parse(readFileSync(0, 'utf8'))
 
 const result = executeScript(input, script)