gremlins-ts/src/utils/configurable.ts

A monkey testing library written in JavaScript, for Node.js and the browser. Use it to check the robustness of web applications by unleashing a horde of undisciplined gremlins.

/**
 * Make a function configurable
 *
 * Configurable functions modify their configuration. The configuration
 * must be an object defined in the function closure.
 *
 *   var config = {
 *     foo: 1
 *   };
 *   function bar() {
 *      console.log('foo value is', config.foo);
 *   }
 *   bar(); // 'foo value is 1'
 *   config.foo = 3;
 *   bar(); // 'foo value is 3'
 *
 * The configurable behavior modifies the function object, adding one
 * method for each item in the configuration.
 *
 * The added methods use the same name as the configuration items. The
 * added methods are both setters and getters, which means that they return
 * the config value when called without argument, and they modify the
 * config value when called with an argument.
 *
 *   configurable(bar, config);
 *   // Now bar has a foo() method
 *
 *   bar.foo(2)
 *   bar(); // 'foo value is 2'
 *   bar.foo(); // 2
 *
 * @param {Function} targetFunction - The functions to make configurable
 * @param {Object} config - The configuration object with the default config values
 */
export function configurable(
  targetFunction: Function,
  config: { [key: string]: any }
) {
  for (let item in config) {
    (function(item) {
      // @ts-ignore
      targetFunction[item] = function(value: any) {
        if (!arguments.length) {
          return config[item];
        }
        config[item] = value;
        return targetFunction;
      };
    })(item); // for doesn't create a closure, forcing it
  }
}