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    <pre><code>(name is undefined) </code></pre> <p><strong>You:</strong> What is <code>name</code>?<sup> (*)</sup><br> <strong>JavaScript:</strong> <code>name</code>? What's a <code>name</code>? I don't know what you're talking about. You haven't ever mentioned any <code>name</code> before. Are you seeing some other scripting language on the (client-)side?</p> <pre><code>name = null; </code></pre> <p><strong>You:</strong> What is <code>name</code>?<br> <strong>JavaScript:</strong> I don't know.</p> <p>In short; <code>undefined</code> is where no notion of the thing exists; it has no type, and it's never been referenced before in that scope; <code>null</code> is where the thing is known to exist, but it's not known what the value is.</p> <p>One thing to remember is that <code>null</code> is not, conceptually, the same as <code>false</code> or <code>""</code> or such, even if they equate after type casting, i.e.</p> <pre><code>name = false; </code></pre> <p><strong>You:</strong> What is <code>name</code>?<br> <strong>JavaScript:</strong> Boolean false.</p> <pre><code>name = ''; </code></pre> <p><strong>You:</strong> What is <code>name</code>?<br> <strong>JavaScript:</strong> Empty string</p> <hr> <p><sup>*: <code>name</code> in this context is meant as a variable which has never been defined. It could be be any undefined variable. However, name is a property of just about any HTML form element. It goes way, way back and was instituted well before id. It is useful because ids must be unique but names to not have to be. </sup></p>
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    1. POWhy is null an object and what's the difference between null and undefined?
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    1. USKen Kin
    1. USRob
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    1. POWhy is null an object and what's the difference between null and undefined?
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    1. COBut in JavaScript, the empty string '' is still a boolean false.
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      1. USAndreas Grech
    2. COThe empty string is not boolean false, but in the context of a conditional it is interpreted as a false(y) value (coercion).
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      1. USBryan Matthews
    3. COFor the second case, where name = null, instead of 'I don't know', JavaScript could answer: The null object. Other than that I like the style of the answer.
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      1. USJean Vincent
 

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