react-esm/dist-src/shared/invariant.js

React is a JavaScript library for building user interfaces.

/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 */

/**
 * Use invariant() to assert state which your program assumes to be true.
 *
 * Provide sprintf-style format (only %s is supported) and arguments
 * to provide information about what broke and what you were
 * expecting.
 *
 * The invariant message will be stripped in production, but the invariant
 * will remain to ensure logic does not differ in production.
 */
let validateFormat = () => {};

if (__DEV__) {
  validateFormat = function (format) {
    if (format === undefined) {
      throw new Error('invariant requires an error message argument');
    }
  };
}

export default function invariant(condition, format, a, b, c, d, e, f) {
  validateFormat(format);

  if (!condition) {
    let error;

    if (format === undefined) {
      error = new Error('Minified exception occurred; use the non-minified dev environment ' + 'for the full error message and additional helpful warnings.');
    } else {
      const args = [a, b, c, d, e, f];
      let argIndex = 0;
      error = new Error(format.replace(/%s/g, function () {
        return args[argIndex++];
      }));
      error.name = 'Invariant Violation';
    }

    error.framesToPop = 1; // we don't care about invariant's own frame

    throw error;
  }
}