warning.js

/**
 * Copyright (c) 2014-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

'use strict';

/**
 * Similar to invariant but only logs a warning if the condition is not met.
 * This can be used to log issues in development environments in critical
 * paths. Removing the logging code for production environments will keep the
 * same logic and follow the same code paths.
 */

var __DEV__ = process.env.NODE_ENV !== 'production';

var warning = function() {};

if (__DEV__) {
  var printWarning = function printWarning(format, args) {
    var len = arguments.length;
    args = new Array(len > 1 ? len - 1 : 0);
    for (var key = 1; key < len; key++) {
      args[key - 1] = arguments[key];
    }
    var argIndex = 0;
    var message = 'Warning: ' +
      format.replace(/%s/g, function() {
        return args[argIndex++];
      });
    if (typeof console !== 'undefined') {
      console.error(message);
    }
    try {
      // --- Welcome to debugging React ---
      // This error was thrown as a convenience so that you can use this stack
      // to find the callsite that caused this warning to fire.
      throw new Error(message);
    } catch (x) {}
  }

  warning = function(condition, format, args) {
    var len = arguments.length;
    args = new Array(len > 2 ? len - 2 : 0);
    for (var key = 2; key < len; key++) {
      args[key - 2] = arguments[key];
    }
    if (format === undefined) {
      throw new Error(
          '`warning(condition, format, ...args)` requires a warning ' +
          'message argument'
      );
    }
    if (!condition) {
      printWarning.apply(null, [format].concat(args));
    }
  };
}

module.exports = warning;