outvariant - npm Package Compare versions

Comparing version 1.2.0 to 1.2.1

lib/invariant.js

@@ -37,7 +37,5 @@ "use strict";
         if (_this.stack) {
-            var prevStack = _this.stack;
-            _this.stack = prevStack
-                .split('\n')
-                .slice(STACK_FRAMES_TO_IGNORE)
-                .join('\n');
+            var nextStack = _this.stack.split('\n');
+            nextStack.splice(1, STACK_FRAMES_TO_IGNORE);
+            _this.stack = nextStack.join('\n');
         }
@@ -44,0 +42,0 @@ return _this;

package.json

 {
   "name": "outvariant",
-  "version": "1.2.0",
+  "version": "1.2.1",
   "description": "Type-safe implementation of invariant with positionals.",
@@ -5,0 +5,0 @@ "main": "lib/index.js",

README.md

 # `outvariant`
 
-## Why?
+Type-safe implementation of invariant with positionals.
 
-- Type-safe implementation of invariant. Asserts the given predicate expression so it's treated as non-nullable after the `invariant` call:
+## Motivation
 
+### Type-safely
+
+This implementation asserts the given predicate expression so it's treated as non-nullable after the `invariant` call:
+
 ```ts
-// Regular "invariant":
+// Regular invariant:
 invariant(user, 'Failed to fetch')
 user?.firstName // "user" is possibly undefined
 
-// The glorious "outvariant":
+// Outvariant:
 invariant(user, 'Failed to fetch')
-user.firstName // OK, "user" exists at this point
+user.firstName // OK, "invariant" ensured the "user" exists
 ```
 
-- Positionals support.
+### Positionals support
 
+This implementation uses [rest parameters](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/rest_parameters) to support dynamic number of positionals:
+
 ```js
@@ -23,4 +29,26 @@ invariant(predicate, 'Expected %s but got %s', 'one', false)
 
-## Getting started
+## What is this for?
 
+Invariant is a shorthand function that asserts a given predicate and throws an error if that predicate is false.
+
+Compare these two pieces of code identical in behavior:
+
+```js
+if (!token) {
+  throw new Error(`Expected a token to be set but got ${typeof token}`)
+}
+```
+
+```js
+import { invariant } from 'outvariant'
+
+invariant(token, 'Expected a token to be set but got %s', typeof token)
+```
+
+Using `invariant` reduces the visual nesting of the code and leads to cleaner error messages thanks to formatted positionals (i.e. the `%s` (string) positional above).
+
+## Usage
+
+### Install
+
 ```sh
@@ -32,2 +60,6 @@ npm install outvariant
 
+> You may want to install this library as a dev dependency (`-D`) based on your usage.
+
+### Write an assertion
+
 ```js
@@ -38,1 +70,32 @@ import { invariant } from 'outvariant'
 ```
+
+## Positionals
+
+The following positional tokens are supported:
+
+| Token     | Expected value type                                     |
+| --------- | ------------------------------------------------------- |
+| `%s`      | String                                                  |
+| `%d`/`%i` | Number                                                  |
+| `%j`      | JSON (non-stringified)                                  |
+| `%o`      | Arbitrary object or object-like (i.e. a class instance) |
+
+Whenever present in the error message, a positional token will look up the value to insert in its place from the arguments given to `invariant`.
+
+```js
+invariant(
+  false,
+  'Expected the "%s" property but got %j',
+  // Note that positionals are sensitive to order:
+  // - "firstName" replaces "%s" because it's first.
+  // - {"id":1} replaces "%j" because it's second.
+  'firstName',
+  {
+    id: 1,
+  }
+)
+```
+
+## Contributing
+
+Please [open an issue](https://github.com/open-draft/outvariant/issues) or [submit a pull request](https://github.com/open-draft/outvariant/pulls) if you wish to contribute. Thank you.

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Improved metrics

Total package byte prevSize

8681

increased by30.29%

Number of lines in readme file

99

increased by175%

Worsened metrics

Lines of code

133

decreased by-1.48%

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