Add babel

.eslintrc

@@ -0,0 +1,9 @@
+{
+  "parser": "babel-eslint",
+  "extends": ["eslint:recommended", "plugin:prettier/recommended"],
+  "env": {
+    "jest": true,
+    "browser": true,
+    "node": true
+  }
+}

babel.config.js

@@ -0,0 +1,13 @@
+module.exports = {
+    presets: [
+        [
+            '@babel/preset-env',
+            {
+                targets: {
+                    node: 'current',
+                },
+            },
+        ],
+    ],
+    plugins: ['@babel/plugin-proposal-class-properties'],
+}

jest.config.js

@@ -1,31 +1,22 @@
 module.exports = {
-  coverageDirectory: './coverage',
-  coveragePathIgnorePatterns: [
-    '/node_modules/',
-    '/lib/',
-    '/esm/',
-  ],
-  coverageReporters: [
-    'lcov',
-  ],
-  reporters: ["default", "jest-junit"],
-  globals: {
-    __DEV__: true,
-    'ts-jest': {
-      babelConfig: true,
+    coverageDirectory: './coverage',
+    coveragePathIgnorePatterns: ['/node_modules/', '/lib/', '/esm/'],
+    coverageReporters: ['lcov'],
+    reporters: ['default', 'jest-junit'],
+    globals: {
+        __DEV__: true,
+        'ts-jest': {
+            babelConfig: true,
+        },
     },
-  },
-  roots: [
-    './src',
-    './tests',
-  ],
-  setupFiles: [],
-  setupFilesAfterEnv: null,
-  testRegex: '(/__tests__/.*|(\\.|/)(test|spec))\\.(jsx?|tsx?)$',
-  transform: {
-    '^.+\\.ts?$': 'ts-jest',
-  },
-  verbose: false,
-  preset: 'ts-jest',
-  testMatch: null,
-}
+    roots: ['./src', './tests'],
+    setupFiles: [],
+    setupFilesAfterEnv: null,
+    testRegex: '(/__tests__/.*|(\\.|/)(test|spec))\\.(jsx?|tsx?)$',
+    transform: {
+        '^.+\\.ts?$': 'ts-jest',
+    },
+    verbose: false,
+    preset: 'ts-jest',
+    testMatch: null,
+}