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<p> This script can handle hundreds of concurrent requests while using |
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little CPU or memory—<a href="#benchmarks">see benchmarks</a>. |
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Check out <a href="#api">the documentation</a> for more examples. |
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<p> Check out <a href="#api">the API documentation</a> for more examples. |
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<p> Node is free to <a href="#download">download</a>, <a |
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href="#api">use</a>, and <a href="#modules">build upon</a>.</p> |
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<h3>Evented Programming Makes More Sense</h3> |
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difference between blocking/non-blocking design
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Difference between blocking/non-blocking design
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<p> There are many methods to write internet servers but they can |
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fundamentally be divided into two camps: evented and threaded; non-blocking |
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<h3 id="modules">Modules</h3> |
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<p>Node has simple module loading. Here is an example. This is the file |
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<code>foo.js</code>: |
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<p>Node has a simple module loading system. In Node, files and modules are |
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in one-to-one correspondence. |
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<p> As an example, |
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<code>foo.js</code> loads the module <code>mjsunit.js</code>. |
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<p>The contents of <code>foo.js</code>: |
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<pre> |
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include("mjsunit");
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function onLoad () {
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assertEquals(1, 2); |
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} |
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</pre> |
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<p>Here the module <code>mjsunit</code> has provided the function |
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<code>assertEquals()</code>. |
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<p> The module file, <code>mjsunit.js</code>, must be in the same directory |
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as <code>foo.js</code> for <code>include()</code> to work. The |
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<code>include()</code> function will insert all the exported objects from the |
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module into the global namespace. |
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<p> Because file loading does not happen instantaneously, and because Node |
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has a policy of never blocking, the callback <code>onLoad()</code> is |
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provided to notify the user when all the exported functions are completely |
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loaded. |
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<p> To export an object, add to the special object <code class="highlight">exports</code>. |
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Let's look at how <code>mjsunit.js</code> does this |
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<p>The contents of <code>mjsunit.js</code>: |
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<pre> |
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function fail (expected, found, name_opt) {
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// ... |
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} |
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function deepEquals (a, b) {
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// ... |
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} |
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<span class="highlight">exports</span>.assertEquals = function (expected, found, name_opt) {
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if (!deepEquals(found, expected)) {
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fail(expected, found, name_opt); |
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} |
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}; |
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</pre> |
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<p>Here the module <code>mjsunit.js</code> has exported the function |
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<code>assertEquals()</code>. <code>mjsunit.js</code> must be in the |
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same directory as <code>foo.js</code> for <code>include()</code> to find it. |
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The module path is relative to the file calling <code>include()</code>. |
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The module path does not include filename extensions like <code>.js</code>. |
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<p> <code>include()</code> inserts the exported objects |
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from the specified module into the global namespace. |
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<p> Because file loading does not happen instantaneously, and because Node |
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has a policy of never blocking, the callback <code>onLoad()</code> is |
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provided to notify the user when all the included modules are loaded. |
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Each file can have its own <code>onLoad()</code> callback. |
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<code>onLoad()</code> will always be called exactly once for each file. |
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<p> To export an object, add to the special <code |
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class="highlight">exports</code> object. |
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<p> The functions <code>fail</code> and <code>deepEquals</code> are not |
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exported and remain private to the module. |
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<p> In addition to <code>include()</code> a module can use |
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<code>require()</code>. Instead of loading the exported objects into the |
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global namespace, it will return a namespace object. Again, the members of
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the namespace object can only be guaranteed to exist after the
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<code>onLoad()</code> callback is made. For example:
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global namespace, it will return a namespace object. The exported objects
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can only be guaranteed to exist after the <code>onLoad()</code> callback is
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made. For example: |
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<pre> |
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var mjsunit = require("mjsunit");
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} |
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</pre> |
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<p> <code>include()</code> and <code>require()</code> cannot be used after |
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<code>onLoad()</code> is called. So put them at the beginning of your file. |
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</body> |
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</html> |
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