Introduction-to-Accessing-the-MLB-AM-API/section4.html at master · MarcoSchermers/Introduction-to-Accessing-the-MLB-AM-API · GitHub

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<!DOCTYPE html>
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    Micheal Willard
    CS 290-400
    Winter 2015
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    <title>MLBAM API How-To</title>

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        <!-- <h1 class="blog-title">Introduction to Accessing the MLBAM API</h1>
        <p class="lead blog-description">by Micheal Willard</p> -->
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            <h2 class="blog-post-title">Section 4: Accessing the Scoreboard Data Using Javascript</h2>
            <hr>
            <h3>Making the AJAX Call</h3>
            <p>
              I'm now going to walk through the code that will generate a very simplistic scoreboard for a <b>selected day</b> that is built off of the <b>minscoreboard.json</b> data.  Let's assume we are going to access the Day Level Folder using Javascript and an AJAX call (the method for PHP is very similar).  The first thing we will need is a function for making the AJAX call to the API.  The <code>getScores()</code> function is triggered by an HTML submit button.
          </p>
          <pre><code>function getScores() {
            var emptyNode = document.getElementById('scoreboard');
            emptyNode.innerHTML = '';
            var req = new XMLHttpRequest();
            if(!req) {
              throw 'Unable to create HttpRequest.';
            }
            var yearSelect = document.getElementsByName('year')[0].value;
            var monthSelect = document.getElementsByName('month')[0].value;
            var daySelect = document.getElementsByName('day')[0].value;
            var url = 'http://gd2.mlb.com/components/game/mlb/';
            url += 'year_' + yearSelect + '/month_' + monthSelect + '/day_' + daySelect + '/miniscoreboard.json';
            req.onreadystatechange = function() {
              if(this.readyState === 4) {
                if(this.status === 200) {
                  var response = JSON.parse(this.responseText);
                  createScoreboard(document.getElementById('scoreboard'), response);
                }
              }
            };
            req.open('GET', url);
            req.send();
          }
        </code></pre>
        <p>
          The <code>yearSelect</code>, <code>monthSelect</code>, <code>daySelect</code> can be variables input by the user through an HTML form or another method.  We can see the base URL at <code>url = 'http://gd2.mlb.com/components/game/mlb/';</code>.  The URL the concatenates the year, month, day and <b>miniscoreboard.json</b> filename.</p>
          <p> Next, we parse the JSON we have received with: <pre><code>var response = JSON.parse(this.responseText);</code></pre>  Finally, a function is called to handle the return value: <pre><code>createScoreboard(document.getElementById('scoreboard'), response);</code></pre>
        </p>
        <h3>Making a Game Object</h3>
        <p>
          Taking an Object Oriented approach, we can simplify the process of outputting the scoreboard data.  So let's create and Object called <b>Game</b> which will represent each game that day.
        </p>
        <pre><code>function Game() {
          this.homeTeam = '';
          this.awayTeam = '';
          this.homeScore = '';
          this.awayScore = '';
          // Setters
          this.setHomeTeam = function(homeTeam) {
            this.homeTeam = homeTeam;
          };
          this.setAwayTeam = function(awayTeam) {
            this.awayTeam = awayTeam;
          };
          this.setHomeScore = function(homeScore) {
            this.homeScore = homeScore;
          };
          this.setAwayScore = function(awayScore) {
            this.awayScore = awayScore;
          };
          // Getters
          this.getHomeTeam = function(homeTeam) {
            return this.homeTeam;
          };
          this.getAwayTeam = function(awayTeam) {
            return this.awayTeam;
          };
          this.getHomeScore = function(homeScore) {
            return this.homeScore;
          };
          this.getAwayScore = function(awayScore) {
            return this.awayScore;
          };
        }</code></pre>
        <h3>Populate the Object</h3>
        <p>
          The Game Objects will need to be populated.  We have called the <code>createScoreboard()</code> function within the <code>getScores()</code> function.  This function takes the 2 parameters:
          <ul>
           <li><code>scoreTable</code> is an HTML element where the scoreboard will be displayed.</li>
            <li><code>response</code> is the parse JSON responseText we received.</li>
          </ul>
          We set the <b>obj</b> variable to step down the tiers of attributes we saw in Section 3.  Then all that is needed is to call a for-in loop to grab each attribute we are looking for and set the value using the <b>Setter</b> functions in the Game Object.  FInally, <code>tableObject()</code> is called to place the new Game object into an HTML Table Element.
        </p>
        <pre><code>function createScoreboard(scoreTable, response) {
          var obj = response.data.games.game;
          for (var key in obj) {
              var tempItem = new Game();
              tempItem.setHomeTeam(obj[key].home_team_name);
              tempItem.setAwayTeam(obj[key].away_team_name);
              tempItem.setHomeScore(obj[key].home_team_runs);
              tempItem.setAwayScore(obj[key].away_team_runs);
              tableObject(scoreTable, tempItem);
          }
        }</code></pre>
        <h3>Building Table Elements</h3>
        <p>
          I won't go into too much detail on the <code>tableObject()</code> as it is pretty specific to this application.  What it does though is utilize the <b>Getter</b> functions to create HTML Table Elements and populate them with the Game Object data.
        </p>
        <pre><code>function tableObject(scoreTable, tempItem) {
          var newTable = document.createElement('table');
          var tblBody = document.createElement('tbody');

          // Build the Away Team Name and Score
          var row1 = document.createElement('tr');

          var th1 = document.createElement('th');
          var th1Text = document.createTextNode(tempItem.getAwayTeam());
          th1.appendChild(th1Text);
          row1.appendChild(th1);

          var td1 = document.createElement('td');
          var td1Text = document.createTextNode(tempItem.getAwayScore());
          td1.appendChild(td1Text);
          row1.appendChild(td1);
          tblBody.appendChild(row1);

          // Build the Home Team Name and Score
          var row2 = document.createElement('tr');

          var th2 = document.createElement('th');
          var th2Text = document.createTextNode(tempItem.getHomeTeam());
          th2.appendChild(th2Text);
          row2.appendChild(th2);

          var td2 = document.createElement('td');
          var td2Text = document.createTextNode(tempItem.getHomeScore());
          td2.appendChild(td2Text);
          row2.appendChild(td2);
          tblBody.appendChild(row2);

          newTable.appendChild(tblBody);
          scoreTable.appendChild(newTable);
          newTable.setAttribute("class", "table table-bordered");
        }</code></pre>
        <h2>Click "Next" to Demo the Code!</h2>

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          <div class="sidebar-module sidebar-module-inset">
            <h4>About</h4>
            <p>This site offers a How-To on accessing the MLB Advanced Media Api.  The code is all done in Javascript, but PHP has similar methods which can be applied to attain the same effect if server side scripting is desired.</p>
          </div>
          <div class="sidebar-module">
            <h4>Sections</h4>
            <ol class="list-unstyled">
              <li><a href="section1.html">Section 1: The Structure of the API Data</a></li>
              <li><a href="section2.html">Section 2: The Date Level Folder</a></li>
              <li><a href="section3.html">Section 3: The Scoreboard JSONs</a></li>
              <li><a href="example.html">Section 5: A Scoreboard Example Using Javascript</a></li>
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        <h4>Elsewhere</h4>
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          <li><a href="https://github.com/michealwillard">GitHub</a></li>
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