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    <p><strong>Values</strong> are immutable; <strong>variables</strong> are not; they hold a reference to their (primitive) values.</p> <p>The three primitive types <em>string, number and boolean</em> have corresponding types whose instances are objects: <em>String, Number, Boolean</em>.<br> They are sometimes called <em><a href="https://developer.mozilla.org/en-US/docs/Glossary/Primitive" rel="noreferrer">wrapper types</a></em>. </p> <p>The following values are <a href="https://developer.mozilla.org/en-US/docs/Glossary/Primitive" rel="noreferrer">primitive</a>: </p> <ul> <li>Strings: "hello"</li> <li>Numbers: 6, 3.14 (all numbers in JavaScript are floating point)</li> <li>Booleans: true, false</li> <li>null: usually explicitly assigned</li> <li>undefined: usually the default (automatically assigned) value</li> </ul> <p>All other values are objects, including wrappers for primitives. </p> <p>So:</p> <ul> <li>Objects are mutable by default</li> <li>Objects have unique identities and are compared by reference</li> <li>Variables hold references to objects</li> <li>Primitives are immutable</li> <li>Primitives are compared by value, they don’t have individual identities</li> </ul> <p>You might find <a href="http://javascriptweblog.wordpress.com/2010/09/27/the-secret-life-of-javascript-primitives/" rel="noreferrer">The Secret Life of JavaScript Primitives</a> a good explanation.</p> <p>Also, in ES6 there is a new <a href="https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Statements/const" rel="noreferrer">const</a> keyword, that creates a read-only named constant that cannot change value through assignment or be re-declared while the script is running.</p> <p>Hope this helps!</p>
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    1. COThanks it helps. But I don't know what unique identity is.. Also, can I find more analytical info about how primitives are associated with these wrappers? Just seems strange to me that i can call a method on primitives (eg aString.length).
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      1. USAntonis Grigoriadis
    2. COThe ***wrapper*** has the method `length`. Note the casing in the second line of my answer.     This [link: The Secret Life of JavaScript Primitives](http://javascriptweblog.wordpress.com/2010/09/27/the-secret-life-of-javascript-primitives/) might help a lot!
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