[Build]: add type-check to npm scripts and ci

package.json

@@ -7,8 +7,9 @@
   "scripts": {
     "coveralls": "cat ./reports/coverage/lcov.info | coveralls",
     "lint": "eslint ./",
-    "pretest": "npm run lint",
+    "pretest": "npm run lint && npm run type-check",
     "test": "npm run unit-test",
+    "type-check": "tsc",
     "unit-test": "istanbul cover --dir reports/coverage node_modules/mocha/bin/_mocha tests/lib/**/*.js tests/util/**/*.js tests/index.js"
   },
   "files": [

tsconfig.json

@@ -0,0 +1,21 @@
+{
+  "compilerOptions": {
+    "target": "ES2015",       /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019' or 'ESNEXT'. */
+    "module": "commonjs",     /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. */
+    "lib": ["es2016"],        /* Specify library files to be included in the compilation. */
+    "allowJs": true,          /* Allow javascript files to be compiled. */
+    "checkJs": true,          /* Report errors in .js files. */
+    "noEmit": true,           /* Do not emit outputs. */
+
+    /* Strict Type-Checking Options */
+    // "strict": true,                           /* Enable all strict type-checking options. */
+    // "noImplicitAny": false,                 /* Raise error on expressions and declarations with an implied 'any' type. */
+    // "strictNullChecks": true,              /* Enable strict null checks. */
+    // "strictFunctionTypes": true,           /* Enable strict checking of function types. */
+    // "strictBindCallApply": true,           /* Enable strict 'bind', 'call', and 'apply' methods on functions. */
+    // "strictPropertyInitialization": true,  /* Enable strict checking of property initialization in classes. */
+    // "noImplicitThis": true,                /* Raise error on 'this' expressions with an implied 'any' type. */
+    // "alwaysStrict": true,                  /* Parse in strict mode and emit "use strict" for each source file. */
+  },
+  "include": ["lib"],
+}