@serenity-js/core/lib/io/reflection/has.js

The core Serenity/JS framework, providing the Screenplay Pattern interfaces, as well as the test reporting and integration infrastructure

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.has = has;
/**
 *  Checks if the `candidate` value "quacks like a duck".
 *  In particular, it checks if the `candidate`:
 *  - is not `null`
 *  - is not `undefined`
 *  - has expected methods or fields (evaluated via [`typeof`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/typeof))
 *
 * ```ts
 *  const looksLikeADuck = has({
 *      name:   'string',
 *      quack:  'function',
 *  })
 *
 *  const daisy = {
 *      name: 'Daisy',
 *      quack: () => 'quack',
 *  }
 *
 *  looksLikeADuck(daisy) // true
 * ```
 *
 * @param api
 *  An object where the keys are names of member fields and methods expected on the `candidate`,
 *  and values are the names of their types, i.e. `function`, `object`, etc.
 */
function has(api) {
    return (candidate) => candidate !== null
        && candidate !== undefined
        && Object.entries(api).reduce((result, [key, type]) => result && (typeof candidate[key]) === type, true);
}
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