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const isProduction: boolean = process.env.NODE_ENV === 'production';
const prefix: string = 'Invariant failed';
// Throw an error if the condition fails
// Strip out error messages for production
// > Not providing an inline default argument for message as the result is smaller
export default function invariant(
condition: any,
// Can provide a string, or a function that returns a string for cases where
// the message takes a fair amount of effort to compute
message?: string | (() => string),
): asserts condition {
if (condition) {
return;
}
// Condition not passed
// In production we strip the message but still throw
if (isProduction) {
throw new Error(prefix);
}
// When not in production we allow the message to pass through
// *This block will be removed in production builds*
const provided: string | undefined = typeof message === 'function' ? message() : message;
// Options:
// 1. message provided: `${prefix}: ${provided}`
// 2. message not provided: prefix
const value: string = provided ? `${prefix}: ${provided}` : prefix;
throw new Error(value);
}