Website : rimsha.abasa.com
backdoor
Home
Console
Upload
information
Create File
Create Folder
About
Tools
:
/
var
/
canvas
/
node_modules
/
tiny-invariant
/
Filename :
README.md
back
Copy
# tiny-invariant 🔬💥 [](https://travis-ci.org/alexreardon/tiny-invariant) [](https://www.npmjs.com/package/tiny-invariant) [](https://david-dm.org/alexreardon/tiny-invariant)  [](https://www.npmjs.com/package/tiny-invariant) [](https://www.npmjs.com/package/tiny-invariant) A tiny [`invariant`](https://www.npmjs.com/package/invariant) alternative. ## What is `invariant`? An `invariant` function takes a value, and if the value is [falsy](https://github.com/getify/You-Dont-Know-JS/blob/bdbe570600d4e1107d0b131787903ca1c9ec8140/up%20%26%20going/ch2.md#truthy--falsy) then the `invariant` function will throw. If the value is [truthy](https://github.com/getify/You-Dont-Know-JS/blob/bdbe570600d4e1107d0b131787903ca1c9ec8140/up%20%26%20going/ch2.md#truthy--falsy), then the function will not throw. ```js import invariant from 'tiny-invariant'; invariant(truthyValue, 'This should not throw!'); invariant(falsyValue, 'This will throw!'); // Error('Invariant violation: This will throw!'); ``` You can also provide a function to generate your message, for when your message is expensive to create ```js import invariant from 'tiny-invariant'; invariant(value, () => getExpensiveMessage()); ``` ## Why `tiny-invariant`? The [`library: invariant`](https://www.npmjs.com/package/invariant) supports passing in arguments to the `invariant` function in a sprintf style `(condition, format, a, b, c, d, e, f)`. It has internal logic to execute the sprintf substitutions. The sprintf logic is not removed in production builds. `tiny-invariant` has dropped all of the sprintf logic. `tiny-invariant` allows you to pass a single string message. With [template literals](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Template_literals) there is really no need for a custom message formatter to be built into the library. If you need a multi part message you can just do this: ```js invariant(condition, `Hello, ${name} - how are you today?`); ``` ## Type narrowing `tiny-invariant` is useful for correctly narrowing types for `flow` and `typescript` ```ts const value: Person | null = { name: 'Alex' }; // type of value == 'Person | null' invariant(value, 'Expected value to be a person'); // type of value has been narrowed to 'Person' ``` ## API: `(condition: any, message?: string | (() => string)) => void` - `condition` is required and can be anything - `message` optional `string` or a function that returns a `string` (`() => string`) ## Installation ```bash # yarn yarn add tiny-invariant # npm npm install tiny-invariant --save ``` ## Dropping your `message` for kb savings! Big idea: you will want your compiler to convert this code: ```js invariant(condition, 'My cool message that takes up a lot of kbs'); ``` Into this: ```js if (!condition) { if ('production' !== process.env.NODE_ENV) { invariant(false, 'My cool message that takes up a lot of kbs'); } else { invariant(false); } } ``` - **Babel**: recommend [`babel-plugin-dev-expression`](https://www.npmjs.com/package/babel-plugin-dev-expression) - **TypeScript**: recommend [`tsdx`](https://github.com/jaredpalmer/tsdx#invariant) (or you can run `babel-plugin-dev-expression` after TypeScript compiling) Your bundler can then drop the code in the `"production" !== process.env.NODE_ENV` block for your production builds to end up with this: ```js if (!condition) { invariant(false); } ``` - rollup: use [rollup-plugin-replace](https://github.com/rollup/rollup-plugin-replace) and set `NODE_ENV` to `production` and then `rollup` will treeshake out the unused code - Webpack: [instructions](https://webpack.js.org/guides/production/#specify-the-mode) ## Builds - We have a `es` (EcmaScript module) build - We have a `cjs` (CommonJS) build - We have a `umd` (Universal module definition) build in case you needed it We expect `process.env.NODE_ENV` to be available at module compilation. We cache this value ## That's it! 🤘