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        <h1 class="page-title">seq.js</h1>
        

        



    
    <section>
        <article>
            <pre class="prettyprint source linenums"><code>import reduce from &apos;./reduce.js&apos;
import wrapAsync from &apos;./internal/wrapAsync.js&apos;
import { promiseCallback, PROMISE_SYMBOL } from &apos;./internal/promiseCallback.js&apos;

/**
 * Version of the compose function that is more natural to read. Each function
 * consumes the return value of the previous function. It is the equivalent of
 * [compose]{@link module:ControlFlow.compose} with the arguments reversed.
 *
 * Each function is executed with the `this` binding of the composed function.
 *
 * @name seq
 * @static
 * @memberOf module:ControlFlow
 * @method
 * @see [async.compose]{@link module:ControlFlow.compose}
 * @category Control Flow
 * @param {...AsyncFunction} functions - the asynchronous functions to compose
 * @returns {Function} a function that composes the `functions` in order
 * @example
 *
 * // Requires lodash (or underscore), express3 and dresende&apos;s orm2.
 * // Part of an app, that fetches cats of the logged user.
 * // This example uses `seq` function to avoid overnesting and error
 * // handling clutter.
 * app.get(&apos;/cats&apos;, function(request, response) {
 *     var User = request.models.User;
 *     async.seq(
 *         User.get.bind(User),  // &apos;User.get&apos; has signature (id, callback(err, data))
 *         function(user, fn) {
 *             user.getCats(fn);      // &apos;getCats&apos; has signature (callback(err, data))
 *         }
 *     )(req.session.user_id, function (err, cats) {
 *         if (err) {
 *             console.error(err);
 *             response.json({ status: &apos;error&apos;, message: err.message });
 *         } else {
 *             response.json({ status: &apos;ok&apos;, message: &apos;Cats found&apos;, data: cats });
 *         }
 *     });
 * });
 */
export default function seq(...functions) {
    var _functions = functions.map(wrapAsync);
    return function (...args) {
        var that = this;

        var cb = args[args.length - 1];
        if (typeof cb == &apos;function&apos;) {
            args.pop();
        } else {
            cb = promiseCallback();
        }

        reduce(_functions, args, (newargs, fn, iterCb) =&gt; {
            fn.apply(that, newargs.concat((err, ...nextargs) =&gt; {
                iterCb(err, nextargs);
            }));
        },
        (err, results) =&gt; cb(err, ...results));

        return cb[PROMISE_SYMBOL]
    };
}
</code></pre>
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    <h3>Methods:</h3><ul class="nav methods"><li class="toc-header"><a href="docs.html#collections">Collections</a></li><li data-type="method" class="toc-method"><a href="docs.html#concat">concat</a></li><li data-type="method" class="toc-method"><a href="docs.html#concatLimit">concatLimit</a></li><li data-type="method" class="toc-method"><a href="docs.html#concatSeries">concatSeries</a></li><li data-type="method" class="toc-method"><a href="docs.html#detect">detect</a></li><li data-type="method" class="toc-method"><a href="docs.html#detectLimit">detectLimit</a></li><li data-type="method" class="toc-method"><a href="docs.html#detectSeries">detectSeries</a></li><li data-type="method" class="toc-method"><a href="docs.html#each">each</a></li><li data-type="method" class="toc-method"><a href="docs.html#eachLimit">eachLimit</a></li><li data-type="method" class="toc-method"><a href="docs.html#eachOf">eachOf</a></li><li data-type="method" class="toc-method"><a 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