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README.md
tiny-invariant
🔬💥
A tiny invariant
alternative.
What is invariant
?
An invariant
function takes a value, and if the value is falsy then the invariant
function will throw. If the value is truthy, then the function will not throw.
import invariant from 'tiny-invariant';
invariant(truthyValue, 'This should not throw!');
invariant(falsyValue, 'This will throw!');
// Error('Invariant violation: This will throw!');
Why tiny-invariant
?
The library: 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 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: invariant(condition, 'Hello, ${name} - how are you today?')
API: (condition: mixed, message?: string) => void
condition
is required and can be anythingmessage
is an optional string
Installation
# yarn
yarn add tiny-invariant
# bash
npm add tiny-invariant --save
Dropping your message
for kb savings!
We recommend using babel-plugin-dev-expression
to remove the message
argument from your invariant
calls in production builds to save kbs!
What it does it turn your code that looks like this:
invariant(condition, 'My cool message that takes up a lot of kbs');
Into this
if (!condition) {
if ('production' !== process.env.NODE_ENV) {
invariant(false, 'My cool message that takes up a lot of kbs');
} else {
invariant(false);
}
}
Your bundler can then drop the code in the "production" !== process.env.NODE_ENV
block for your production builds
Final result:
if (!condition) {
invariant(false);
}
For
rollup
use rollup-plugin-replace and setNODE_ENV
toproduction
and thenrollup
will treeshake out the unused code
Builds
- We have a
es
(EcmaScript module) build (because you know you want to deduplicate this super heavy library) - 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!
🤘