coding-dojo/index.html at master · 2brainschile/coding-dojo · GitHub

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<!doctype html>
<html lang="es">
  <head>
      <meta charset="utf-8" />
      <meta name="viewport" content="width=1024" />
      <meta name="apple-mobile-web-app-capable" content="yes" />
      <title>Lodash FP</title>
      <meta name="description" content="Lodash for FP" />
      <meta name="author" content="Sebastián Schuchhardt" />
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  </head>
  <body class="impress-not-supported">
    <div class="fallback-message">
        <p>Your browser <b>doesn't support the features required</b> by impress.js, so you are presented with a simplified version of this presentation.</p>
        <p>For the best experience please use the latest <b>Chrome</b>, <b>Safari</b> or <b>Firefox</b> browser.</p>
    </div>
    <div id="impress">

    <!-- <article> -->
      <section id="main" class="step" data-x="0" data-y="0">
        <header>
          <h1>Programacion Funcional en Javascript</h1>
          <h2>con Lodash.js</h2>
        </header>
        <pre class="prettyprint">
          <code class="language-javascript">
            import _ from 'lodash';
            // OR
            import find from 'lodash/find';

            </code>
        </pre>
      </section>
      <section id="values" class="step" data-x="0" data-y="1000">
        <header>
          <h1>Las Funciones son Valores</h1>
        </header>
        <p>En un lenguaje donde las funciones pueden ser valores son llamadas <em>first class functions</em></p>
        <p>Funciones pueden ser asignadas a variables y pasadas como argumentos como cualquier otro valor primitivo</p>
        <pre class="prettyprint">
          <code class="language-javascript">
      const add = (x, y) => x + y;
      </code>
        </pre>
      </section>
      <section id="pure" class="step" data-x="0" data-y="2000">
        <header>
          <h1>Funciones puras</h1>
          <h3><em>pure functions</em></h3>
        </header>
        <p>Una funcion pura tiene solo entradas y salidas</p>
        <p>Una funcion pura no muta/cambia a ningun estado</p>
      </section>
      <section id="pure-code1" class="step" data-x="-500" data-y="2500" data-z="-500">
        <pre class="prettyprint">
          <code class="language-javascript">
    const someArray = [1, 2, 3];
    someArray.push(4);</code>
        </pre>
        <p>
          This mutates <code class="language-javascript inline-snippet">someArray</code>.
        </p>
      </section>
      <section id="pure-code2" class="step" data-x="500" data-y="2500" data-z="-500">
        <pre class="prettyprint">
          <code class="language-javascript">
  const purePush = (item, array) => {
    const newArray = array.slice();
    newArray.push(item);
    return newArray;
  };

  purePush(4, someArray);</code>
        </pre>
        <p>
          Esto retorna un <em>nuevo</em> array y deja
          <code class="language-javascript inline-snippet">someArray</code> sin modificacion
        </p>
      </section>
      <section id="higher-order" class="step" data-x="0" data-y="3300">
        <header>
          <h1>Higher Order Functions</h1>
        </header>
        <p>Una funcion de Alto Orden toma una función como parametro </p>
        <pre class="prettyprint">
          <code class="language-javascript">
        const add1 = (x) => x + 1
        const arr = [1, 2, 3]

        arr.map(add1)
        [2, 3, 4]</code>
        </pre>
      </section>
      <section id="currying" class="step" data-x="0" data-y="4000">
        <header>
          <h1>Currying</h1>
          <h4><em>Llamado parcial de funciones</em></h4>
        </header>
        <p>Cuando no se pasan todos los argumentos de la función:</p>
        <ul>
          <li>Una funcion normal en Javascript sustituye por undefined el resto</li>
          <li>Una curried function returns a <em>partially applied function</em> that accepts the rest</li>
          <li>A curried function returns a <em>partially applied function</em> that accepts the rest</li>
        </ul>
      </section>
      <section id="currying-code" class="step" data-x="0" data-y="4500" data-z="-500">
        <pre class="prettyprint">
          <code class="language-javascript">
        > const add = (x) => {
            return (y) => {
             return x + y
            };
          };

        > const add2 = add(2);
        > add2(5)
        7</code>
        </pre>
      </section>
      <section id="order" class="step" data-x="0" data-y="5100">
        <header>
          <h1>Argument Order</h1>
        </header>
        <p>Los argumentos iniciales de una funcion son como una configuracion</p>
        <p>El ultimo es usualmente la data con la cual operar</p>
        <p>Esto hace mas facil crear funciones especializadas con currying</p>
      </section>
      <section id="order-example1" class="step" data-x="-1200" data-y="5000" data-z="-500">
        <pre class="prettyprint">
          <code class="language-javascript">
  var getNamed = R.filter(R.has("name"));

  > getNamed([
    {id: 0, name: "foo"},
    {id: 1},
    {id: 2, name: "bar"}
  ]);
  [{id: 0, name: "foo"},
   {id: 2, name: "bar"}]</code>
        </pre>
      </section>
      <section id="order-example2" class="step" data-x="-600" data-y="5700" data-z="-500">
        <pre class="prettyprint">
          <code class="language-javascript">
  var firstNamed = R.find(R.has("name"));

  > firstNamed([
    {id: 0, name: "foo"},
    {id: 1},
    {id: 2, name: "bar"}
  ]);
  {id: 0, name: "foo"}
  </code>
        </pre>
      </section>
      <section id="order-example3" class="step" data-x="600" data-y="5700" data-z="-500">
        <pre class="prettyprint">
          <code class="language-javascript">
  var isEven = function(x) {
    return x % 2 === 0;
  };

  var evensOnly = R.filter(isEven);

  > evensOnly([1, 2, 3, 4, 5]);
  [2, 4]</code>
        </pre>
      </section>
      <section id="order-example4" class="step" data-x="1200" data-y="5000" data-z="-500">
        <pre class="prettyprint">
          <code class="language-javascript">
  var duplicate = function(x) {
    return [x, x];
  };

  var duplicateEach = R.chain(duplicate);

  > duplicateEach([1, 2, 3]);
  [1, 1, 2, 2, 3, 3]</code>
        </pre>
      </section>
      <section id="breather" class="step" data-x="0" data-y="6500">
        <header>
          <h1>Thus Ends Section One</h1>
        </header>
        <p>Let's take a quick break now</p>
      </section>
      <section id="composition-section" class="step" data-x="0" data-y="7000">
        <header>
          <h1>Function Composition</h2>
          <h3><em>putting it all together</em></h3>
        </header>
      </section>
      <section id="composition" class="step" data-x="0" data-y="7700">
        <header>
          <h1>Mathematical Functions</h1>
        </header>
        <p>
          A function of one argument <code class="language-javascript inline-snippet">f(x)</code>
          and another function of one argument <code class="language-javascript inline-snippet">g(x)</code>
          can be <em>composed together</em> to make the function <code class="language-javascript inline-snippet">f(g(x))</code>
        </p>
      </section>
      <section id="composition-example" class="step" data-x="0" data-y="8500">
        <pre class="prettyprint">
          <code class="language-javascript">
  > duplicateEach([1, 2, 3]);
  [1, 1, 2, 2, 3, 3]

  > evensOnly([1, 2, 3, 4, 5]);
  [2, 4]

  var duplicateEvens = R.compose(
    duplicateEach,
    evensOnly
  );

  > duplicateEvens([1, 2, 3, 4, 5]);
  [2, 2, 4, 4]</code>
        </pre>
      </section>
      <section id="exercises-main" class="step" data-x="0" data-y="9300">
        <header>
          <h1>Exercises!</h1>
          <h4><em>not the sweaty kind</em><h4>
        </header>
        <p>Let's tackle some exercises and apply these concepts</p>
        <p>Suppose we're working with a JSON API that provides a giant catalog of users.</p>
        <p>
          Each user has an <code class="language-javascript inline-snippet">id</code>,
          a <code class="language-javascript inline-snippet">name</code>, and
          an <code class="language-javascript inline-snippet">age</code>
        </p>
      </section>
      <section id="exercises-catalog" class="step" data-x="0" data-y="10000">
        <pre class="prettyprint">
          <code class="language-javascript">
  {
    users: [
      {id: 3, name: "Thad", age: 36},
      {id: 5, name: "Lucian", age: 23},
      {id: 2, name: "Justine", age: 29},
      {id: 4, name: "Katie", age: 26},
      {id: 0, name: "Jerold", age: 52},
      {id: 1, name: "Nona", age: 33}
    ]
  }</code>
        </pre>
        <p>
          You can find this catalog in the "exercises" folder of the
          class GitHub repository.
        </p>
      </section>
      <section id="exercise1" class="step" data-x="-600" data-y="10800">
        <header>
          <h1>Sorting by ID</h1>
          <h3><code class="language-javascript inline-snippet">npm run-script ex1</code><h3>
        </header>
        <p>It would be useful to see a list of users sorted by ID</p>
        <p>
          Ramda provides a <code class="language-javascript inline-snippet">sortBy</code>
          function to make this easier.
        </p>
        <p>Note: it's a higher order function!</p>
      </section>
      <section id="exercise1-answer" class="step" data-x="600" data-y="10800">
        <pre class="prettyprint">
          <code class="language-javascript">
  var sortCatalogUsersById = R.compose(
    R.sortBy(R.prop("id")),
    R.prop("users")
  );</code>
        </pre>
      </section>
      <section id="exercise2" class="step" data-x="600" data-y="11600">
        <header>
          <h1>Users With an Even Age</h1>
          <h3><code class="language-javascript inline-snippet">npm run-script ex2</code><h3>
        </header>
        <p>Now for some filtering</p>
        <p>Let's say we want only the users in the catalog with an even age</p>
        <p>
          Tip - if you've got <code class="language-javascript inline-snippet">isEven</code>,
          check out Ramda's <code class="language-javascript inline-snippet">propSatisfies</code>.
        </p>
      </section>
      <section id="exercise2-answer" class="step" data-x="-600" data-y="11600">
        <pre class="prettyprint">
          <code class="language-javascript">
  var isEven = function(x) {
    return x % 2 === 0
  };

  var hasEvenAge = R.propSatisfies(
    isEven,
    "age"
  );

  var getUsersWithEvenAge = R.compose(
    R.filter(hasEvenAge),
    R.prop("users")
  );</code>
        </pre>
      </section>
      <section id="exercise3" class="step" data-x="-600" data-y="12400">
        <header>
          <h1>Names of the Three Youngest Users</h1>
          <h3><code class="language-javascript inline-snippet">npm run-script ex3</code><h3>
        </header>
        <p>Instead of sorting by ID, let's sort by age</p>
        <p>Additionally, let's get the 3 youngest users instead of all of them</p>
        <p>As a final twist - let's only get their names, not the whole user objects</p>
      </section>
      <section id="exercise3-answer" class="step" data-x="600" data-y="12400">
        <pre class="prettyprint">
          <code class="language-javascript">
  var getNamesOfThreeYoungestUsers =
    R.compose(
      R.map(R.prop("name")),
      R.take(3),
      R.sortBy(R.prop("age")),
      R.prop("users")
  );</code>
        </pre>
      </section>
      <section id="exercise4" class="step" data-x="600" data-y="13200">
        <header>
          <h1>Users in their Thirties</h1>
          <h3><code class="language-javascript inline-snippet">npm run-script ex4</code><h3>
        </header>
        <p>
          Now a somewhat more complex query - let's get all
          the users with age 30-39
        </p>
        <p>
          Ramda provides <code class="language-javascript inline-snippet">R.lt</code>,
          and <code class="language-javascript inline-snippet">R.gt</code>
          for comparing, but their argument order makes things tricky
        </p>
        <p>
          Maybe try
          <code class="language-javascript inline-snippet">R.flip</code>
          or <code class="language-javascript inline-snippet">R.__</code>
        </p>
      </section>
      <section id="exercise4-answer" class="step" data-x="-600" data-y="13200">
        <pre class="prettyprint">
          <code class="language-javascript">
  var isInThirties = R.both(
    R.gte(R.__, 30),
    R.lt(R.__, 40)
  );

  var userIsInThirties = R.propSatisfies(
    isInThirties,
    "age"
  );

  var getUsersInTheirThirties = R.compose(
    R.filter(userIsInThirties),
    R.prop("users")
  );</code>
        </pre>
      </section>
      <section id="final" class="step" data-x="0" data-y="14000">
        <header>
          <h1>Congratulations!</h1>
          <h3><em>you survived!</em></h3>
        </header>
        <p>Now you know the main techniques of functional programming in Javascript</p>
      </section>
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