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copied!<p>Semicolons after <em>function declarations</em> are <strong>not necessary</strong>.</p> <p>The grammar of a <code>FunctionDeclaration</code> is described in <a href="http://ecma262-5.com/ELS5_HTML.htm#Section_13" rel="noreferrer">the specification</a> as this:</p> <pre><code>function Identifier ( FormalParameterListopt ) { FunctionBody } </code></pre> <p>There's no semicolon grammatically required, but might wonder why?</p> <p>Semicolons serve to separate <em>statements</em> from each other, and a <code>FunctionDeclaration</code> is not a <em>statement</em>.</p> <p><code>FunctionDeclarations</code> are evaluated <em>before</em> the code enters into execution, <a href="https://stackoverflow.com/questions/1710424/referencing-a-javascript-value-before-it-is-declared-can-someone-explain-this/1710509#1710509">hoisting</a> is a <em>common word</em> used to explain this behaviour.</p> <p>The terms "function declaration" and "function statement" are often wrongly used interchangeably, because there is no function statement described in the ECMAScript Specification, however there are some implementations that include a function statement in their grammar, -notably Mozilla- but again this is non-standard.</p> <p>However semicolons are always recommended where you use <code>FunctionExpressions</code>, for example:</p> <pre><code>var myFn = function () { //... }; (function () { //... })(); </code></pre> <p>If you omit the semicolon after the first function in the above example, you will get completely undesired results:</p> <pre><code>var myFn = function () { alert("Surprise!"); } // <-- No semicolon! (function () { //... })(); </code></pre> <p>The first function will be executed immediately, because the parentheses surrounding the second one, will be interpreted as the <code>Arguments</code> of a function call.</p> <p>Recommended lectures:</p> <ul> <li><a href="http://kangax.github.com/nfe/" rel="noreferrer">Named function expressions demystified</a> (great article)</li> <li><a href="https://stackoverflow.com/questions/1634268/explain-javascripts-encapsulated-anonymous-function-syntax">Explain JavaScript’s encapsulated anonymous function syntax</a> (more on <code>FunctionDeclaration</code> vs <code>FunctionExpression</code>)</li> </ul>

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