Error when calling JavaScript function — "can't find variable"
<p>I'm attempting to complete and exercise from the JavaScript Bible, and am having trouble getting my script to function.</p>

<p>The assignment is to create a page that allows users to query a planet's name, and, via a script that matches the planet's name with its data stored in the associate arrays, call up its distance and diameter information.</p>

<p>I'm attempting to call the function 'getPlanetInfo' via a button (onclick='getPlanetInfo()'). However, my error console reports that it cannot find a variable named 'getPlanetInfo' when I attempt to run it.</p>

<p>I've attached both my JS and HTML code below. Any idea as to why my function isn't being properly called would be hugely appreciated.</p>

<p>HTML:</p>

<pre><code>&lt;!DOCTYPE html&gt;
&lt;html&gt;
&lt;head&gt;
    ...
    &lt;script type="text/javascript" src="planets.js"&gt;&lt;/script&gt;
&lt;/head&gt;
&lt;body&gt;
        &lt;h1&gt;Check a planet's distance from the sun and its diameter!&lt;/h1&gt;
        &lt;form&gt;
            &lt;input type="text" name="entry" id="entry"&gt;
            &lt;input type="button" value="Check it!" onClick="getPlanetInfo()"&gt;
        &lt;/form&gt;
&lt;/body&gt;
&lt;/html&gt;
</code></pre>

<p>JS:</p>

<pre><code>var planetNames = new Array(4);
planetNames[0] = "Mercury";
planetNames[1] = "Venus";
planetNames[2] = "Earth";
planetNames[3] = "Mars";

var planetDistances = new Array(4);
planetDistances[0] = "36 million miles";
planetDistances[1] = "67 million miles";
planetDistances[2] = "93 million miles";
planetDistances[3] = "141 million miles";

var planetDiameters = new Array(4);
planetDiameters[0] = "3,100 miles";
planetDiameters[1] = "7,700 miles";
planetDiameters[2] = "7,920 miles";
planetDiameters[3] = "4,200 miles";

function getPlanetInfo()
{
var selectedPlanet = document.getElementById("entry").value;
for (var i = 0; i &lt; planetNames.length; i++)
{
    if (planetNames[i] == selectedPlanet)
    {
        break;
    }
}

if (i &lt; planetNames.length)
{
    alert(selectedPlanet + " is " + planetDistances[i] " in distance from the Sun and " + planetDiameters[i] + "in diameter.")
}

else
{
    alert("Sorry, " + selectedPlanet + " isn't in the database.");
}
}
</code></pre>
