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POJavascript object/namespaces - how to access properties added from nested functions (example included)
 

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  1. POJavascript object/namespaces - how to access properties added from nested functions (example included)
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    <p>I've been working on understanding Javascript objects and namespaces and I am a little confused by how we can generate/display object using nested functions. I don't understand how I can nest functions to basically create object factories and display them in the page. Example below.</p> <p>I have tried RTFG and some of the examples on this site, but nothing seems applicable. Any links to relevant Q&amp;A appreciated. but I am hoping an experienced person can explain this behavior.</p> <p>The below three files constitute a simple app to load an index.html page with three car entries, generated by calling a getCar() function three times and setting custom attributes, then adding an engine using a function which itself uses a (completely wrong) function to calculate horsepower. </p> <p>I'd expect to be able to access properties of the returned car1, car2, car3 objects in the HTML but when I load index.html from below in a browser, I see no errors in the Javascript but I don't expect these results:</p> <pre><code>1. undefined &lt;-- this is defined, I set the name in the call from the updatePage() function 2. [object Object] &lt;-- the name is not an object, it's a primitive 3. {"name":"","engine":"","wheels":"","options":"none"} &lt;-- this has properties set, why not show them? </code></pre> <p>Also understanding if I use namespaces, one for car and one for engine, would I need to declare them both at the top of each file like so:</p> <pre><code>var car = car || {} var engine = engine || {} </code></pre> <p>and then reference the calls from carFactory.js with:</p> <pre><code>engine.getEngine(); </code></pre> <p>Like I said, appreciate any help. I am just trying to understand, this is not a class assignment. I have looked at the sections in JavaScript sixth edition and can't see how this namespacing/object setup would work in practice. Apprecate any help.</p> <p>index.html</p> <pre><code>&lt;!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"&gt; &lt;html&gt; &lt;head&gt; &lt;meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"&gt; &lt;title&gt;Object example&lt;/title&gt; &lt;/head&gt; &lt;body&gt; &lt;div id="input"&gt; &lt;p id='intro'&gt;Object-Namespace Example&lt;/p&gt; &lt;input type='button' onclick='updatePage()' value='New Car'/&gt; &lt;/div&gt; &lt;div id="cars"&gt; &lt;div id="car1"&gt;car1&lt;/div&gt; &lt;div id="car2"&gt;car2&lt;/div&gt; &lt;div id="car3"&gt;car3&lt;/div&gt; &lt;/div&gt; &lt;div id="jslib"&gt; &lt;script type="text/javascript" src="carFactory.js"&gt;&lt;/script&gt; &lt;script type="text/javascript" src="engineFactory.js"&gt;&lt;/script&gt; &lt;script type="text/javascript"&gt; function updatePage() { var car1 = getNewCar("Dodge"); var oldHTML = document.getElementById('car1').innerHTML; var newHTML = "&lt;span&gt;" + car1["name"] + "&lt;/span&gt;"; document.getElementById('car1').innerHTML = newHTML; var car2 = getNewCar("Toyota"); var oldHTML = document.getElementById('car2').innerHTML; var newHTML = "&lt;span&gt;" + car2 + "&lt;/span&gt;"; document.getElementById('car2').innerHTML = newHTML; var car3 = getNewCar("Hudson"); var oldHTML = document.getElementById('car3').innerHTML; var newHTML = "&lt;span&gt;" + JSON.stringify(car3) + "&lt;/span&gt;"; document.getElementById('car3').innerHTML = newHTML; }; &lt;/script&gt; &lt;/div&gt; &lt;/body&gt; &lt;/html&gt; </code></pre> <p>carFactory.js</p> <pre><code>function getNewCar(dName) { this.retValue=""; var theCar = new car; theCar.setProp("name",dName); theCar.setProp("engine",getEngine()); theCar.setProp("wheels",4); return theCar; }; car = function() { this.name=""; this.engine=""; this.wheels=""; this.options="none"; this.setProp=function(prop,val) { this[prop]=val; } }; </code></pre> <p>engineFactory.js</p> <pre><code>getEngine = function() { var theEngine = new engine(); theEngine.setProp["cylinders"] = 8; theEngine.setProp["capacity"]=400; theEngine.setProp["fuel"]="injected"; return theEngine; }; engine = function() { this.capacity=""; this.fuel=""; this.cylinder=""; this.nitrous="no"; this.horsepower=getHorsepower(this); this.setProp=function(prop,val) { this[prop]=val; } } function getHorsepower(engine) { this.retValue=0; this.retValue=engine.cylinder*engine.capacity; return this.retValue; } </code></pre>
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    1. COIt's a typo - use either `car` or `car1` ` = getNewCar('Dodge')`
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      1. POJavascript object/namespaces - how to access properties added from nested functions (example included)
      1. USJibi Abraham
 

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