Merge pull request #1 from github/initial-impl

Initial implementation

Author: keithamus

.editorconfig

@@ -0,0 +1,10 @@
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+indent_style = space
+indent_size = 2
+max_line_length = 120
+trim_trailing_whitespace = true
+insert_final_newline = true

.eslintrc.json

@@ -0,0 +1,39 @@
+{
+  "root": true,
+  "plugins": ["github"],
+  "extends": ["plugin:github/recommended", "plugin:github/typescript", "plugin:github/browser"],
+  "rules": {
+    "no-invalid-this": "off",
+    "@typescript-eslint/no-invalid-this": ["error"],
+    "import/extensions": ["error", "ignorePackages"],
+    "import/no-namespace": "off",
+    "import/no-unresolved": "off",
+    "@typescript-eslint/consistent-type-imports": ["error", {"prefer": "type-imports"}]
+  },
+  "overrides": [
+    {
+      "files": "test/*",
+      "rules": {
+        "@typescript-eslint/no-empty-function": "off"
+      },
+      "globals": {
+        "chai": false,
+        "expect": false
+      },
+      "env": {
+        "mocha": true
+      }
+    },
+    {
+      "files": "*.cjs",
+      "env": {
+        "node": true
+      },
+      "rules": {
+        "import/no-commonjs": "off",
+        "filenames/match-regex": "off",
+        "@typescript-eslint/no-var-requires": "off"
+      }
+    }
+  ]
+}

.gitignore

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+lib/
+node_modules/

CODEOWNERS

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+* @github/web-systems-reviewers

README.md

@@ -1,3 +1,51 @@
 # browser-support
 
-Polyfills & Capable Browser detection
+Polyfills for small new features, plus functions to determine browser feature support.
+
+### How is this used on GitHub?
+
+We use all of these polyfills on GitHub.com. We also use the `isSupported()` function to determine if the browser is well supported, unsupported browsers do not send errors or statistics to our backend monitoring.
+
+## Installation
+
+```
+$ npm install @github/browser-support
+```
+
+## Usage
+
+### JS
+
+```js
+import {isSupported, isPolyfilled, apply} from '@github/browser-support'
+
+// Check if a browser is supported
+if (!isSupported()) {
+  apply()
+  console.assert(isSupported() === true)
+  console.assert(isPolyfilled() === true)
+}
+```
+
+## Development
+
+```
+npm install
+npm test
+```
+
+## Contributing
+
+### Adding polyfills
+
+Please do not add any polyfills for ECMA features that are Stage 3 or below. We _only_ wish to polyfill features from ECMAScript that are Stage 4 (about to be included in a new years specification) or already specified.
+
+### Removing polyfills
+
+When our supported browsers (see github/github for details) all support a feature without polyfills, we can remove the polyfill. This code is designed to be kept lightweight, we do not want to ship dozens of kb of polyfills.
+
+As a polyfill is removed, it may be worth adding feature detection to the `baseSupport` const, to ensure that our baseline moves with our browser support matrix.
+
+## License
+
+Distributed under the MIT license. See LICENSE for details.