<span class="token operator">&lt;</span><span class="token operator">!</span><span class="token constant">DOCTYPE</span> html<span class="token operator">&gt;</span>
<span class="token operator">&lt;</span>html<span class="token operator">&gt;</span>
<span class="token operator">&lt;</span>head<span class="token operator">&gt;</span>
<span class="token operator">&lt;</span>script<span class="token operator">&gt;</span>
<span class="token keyword">function</span> <span class="token function">myFunction</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
  document<span class="token punctuation">.</span><span class="token function">getElementById</span><span class="token punctuation">(</span><span class="token string">"demo"</span><span class="token punctuation">)</span><span class="token punctuation">.</span>innerHTML <span class="token operator">=</span> <span class="token string">"Hello World!"</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token operator">&lt;</span><span class="token operator">/</span>script<span class="token operator">&gt;</span>
<span class="token operator">&lt;</span><span class="token operator">/</span>head<span class="token operator">&gt;</span>

<span class="token operator">&lt;</span>body<span class="token operator">&gt;</span>

<span class="token operator">&lt;</span>p<span class="token operator">&gt;</span>When you click <span class="token string">"Try it"</span><span class="token punctuation">,</span> a <span class="token keyword">function</span> will be called<span class="token punctuation">.</span><span class="token operator">&lt;</span><span class="token operator">/</span>p<span class="token operator">&gt;</span>
<span class="token operator">&lt;</span>p<span class="token operator">&gt;</span>The <span class="token keyword">function</span> will display a message<span class="token punctuation">.</span><span class="token operator">&lt;</span><span class="token operator">/</span>p<span class="token operator">&gt;</span>

<span class="token operator">&lt;</span>button onclick<span class="token operator">=</span><span class="token string">"myFunction()"</span><span class="token operator">&gt;</span>Try it<span class="token operator">&lt;</span><span class="token operator">/</span>button<span class="token operator">&gt;</span>

<span class="token operator">&lt;</span>p id<span class="token operator">=</span><span class="token string">"demo"</span><span class="token operator">&gt;</span><span class="token operator">&lt;</span><span class="token operator">/</span>p<span class="token operator">&gt;</span>

<span class="token operator">&lt;</span><span class="token operator">/</span>body<span class="token operator">&gt;</span>
<span class="token operator">&lt;</span><span class="token operator">/</span>html<span class="token operator">&gt;</span>

<span class="token operator">&lt;</span><span class="token operator">!</span><span class="token constant">DOCTYPE</span> html<span class="token operator">&gt;</span>
<span class="token operator">&lt;</span>html<span class="token operator">&gt;</span> 
<span class="token operator">&lt;</span>head<span class="token operator">&gt;</span> 
<span class="token operator">&lt;</span>script<span class="token operator">&gt;</span> 
<span class="token keyword">function</span> <span class="token function">myfunction</span><span class="token punctuation">(</span><span class="token parameter">txt</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> 
  document<span class="token punctuation">.</span><span class="token function">getElementById</span><span class="token punctuation">(</span><span class="token string">"demo"</span><span class="token punctuation">)</span><span class="token punctuation">.</span>innerHTML <span class="token operator">=</span> txt
<span class="token punctuation">}</span> 
<span class="token operator">&lt;</span><span class="token operator">/</span>script<span class="token operator">&gt;</span> 
<span class="token operator">&lt;</span><span class="token operator">/</span>head<span class="token operator">&gt;</span> 
<span class="token operator">&lt;</span>body<span class="token operator">&gt;</span> 

<span class="token operator">&lt;</span>p<span class="token operator">&gt;</span>When you click on one <span class="token keyword">of</span> the buttons<span class="token punctuation">,</span> a <span class="token keyword">function</span> will be called<span class="token punctuation">.</span> The <span class="token keyword">function</span> will display the argument that is passed to it<span class="token punctuation">.</span><span class="token operator">&lt;</span><span class="token operator">/</span>p<span class="token operator">&gt;</span>

<span class="token operator">&lt;</span>form<span class="token operator">&gt;</span> 
  <span class="token operator">&lt;</span>input type<span class="token operator">=</span><span class="token string">"button"</span> onclick<span class="token operator">=</span><span class="token string">"myfunction('Good Morning!')"</span> value<span class="token operator">=</span><span class="token string">"In the Morning"</span><span class="token operator">&gt;</span> 
  <span class="token operator">&lt;</span>input type<span class="token operator">=</span><span class="token string">"button"</span> onclick<span class="token operator">=</span><span class="token string">"myfunction('Good Evening!')"</span> value<span class="token operator">=</span><span class="token string">"In the Evening"</span><span class="token operator">&gt;</span> 
<span class="token operator">&lt;</span><span class="token operator">/</span>form<span class="token operator">&gt;</span> 

<span class="token operator">&lt;</span>p id<span class="token operator">=</span><span class="token string">"demo"</span><span class="token operator">&gt;</span><span class="token operator">&lt;</span><span class="token operator">/</span>p<span class="token operator">&gt;</span>

<span class="token operator">&lt;</span><span class="token operator">/</span>body<span class="token operator">&gt;</span> 
<span class="token operator">&lt;</span><span class="token operator">/</span>html<span class="token operator">&gt;</span>

<span class="token operator">&lt;</span><span class="token operator">!</span><span class="token constant">DOCTYPE</span> html<span class="token operator">&gt;</span>
<span class="token operator">&lt;</span>html<span class="token operator">&gt;</span>
<span class="token operator">&lt;</span>body<span class="token operator">&gt;</span>

<span class="token operator">&lt;</span>h2<span class="token operator">&gt;</span>JavaScript Functions<span class="token operator">&lt;</span><span class="token operator">/</span>h2<span class="token operator">&gt;</span>

<span class="token operator">&lt;</span>p<span class="token operator">&gt;</span>This example calls a <span class="token keyword">function</span> which performs a calculation and returns the result<span class="token operator">:</span><span class="token operator">&lt;</span><span class="token operator">/</span>p<span class="token operator">&gt;</span>

<span class="token operator">&lt;</span>p id<span class="token operator">=</span><span class="token string">"demo"</span><span class="token operator">&gt;</span><span class="token operator">&lt;</span><span class="token operator">/</span>p<span class="token operator">&gt;</span>

<span class="token operator">&lt;</span>script<span class="token operator">&gt;</span>
<span class="token keyword">var</span> x <span class="token operator">=</span> <span class="token function">myFunction</span><span class="token punctuation">(</span><span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
document<span class="token punctuation">.</span><span class="token function">getElementById</span><span class="token punctuation">(</span><span class="token string">"demo"</span><span class="token punctuation">)</span><span class="token punctuation">.</span>innerHTML <span class="token operator">=</span> x<span class="token punctuation">;</span>

<span class="token keyword">function</span> <span class="token function">myFunction</span><span class="token punctuation">(</span><span class="token parameter">a<span class="token punctuation">,</span> b</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
  <span class="token keyword">return</span> a <span class="token operator">*</span> b<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token operator">&lt;</span><span class="token operator">/</span>script<span class="token operator">&gt;</span>

<span class="token operator">&lt;</span><span class="token operator">/</span>body<span class="token operator">&gt;</span>
<span class="token operator">&lt;</span><span class="token operator">/</span>html<span class="token operator">&gt;</span>

<span class="token operator">&lt;</span><span class="token operator">!</span><span class="token constant">DOCTYPE</span> html<span class="token operator">&gt;</span>
<span class="token operator">&lt;</span>html<span class="token operator">&gt;</span>
<span class="token operator">&lt;</span>body<span class="token operator">&gt;</span>

<span class="token operator">&lt;</span>h2<span class="token operator">&gt;</span>JavaScript Functions<span class="token operator">&lt;</span><span class="token operator">/</span>h2<span class="token operator">&gt;</span>

<span class="token operator">&lt;</span>p<span class="token operator">&gt;</span>This example calls a <span class="token keyword">function</span> to convert <span class="token keyword">from</span> Fahrenheit to Celsius<span class="token operator">:</span><span class="token operator">&lt;</span><span class="token operator">/</span>p<span class="token operator">&gt;</span>
<span class="token operator">&lt;</span>p id<span class="token operator">=</span><span class="token string">"demo"</span><span class="token operator">&gt;</span><span class="token operator">&lt;</span><span class="token operator">/</span>p<span class="token operator">&gt;</span>

<span class="token operator">&lt;</span>script<span class="token operator">&gt;</span>
<span class="token keyword">function</span> <span class="token function">toCelsius</span><span class="token punctuation">(</span><span class="token parameter">f</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
  <span class="token keyword">return</span> <span class="token punctuation">(</span><span class="token number">5</span><span class="token operator">/</span><span class="token number">9</span><span class="token punctuation">)</span> <span class="token operator">*</span> <span class="token punctuation">(</span>f<span class="token operator">-</span><span class="token number">32</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
document<span class="token punctuation">.</span><span class="token function">getElementById</span><span class="token punctuation">(</span><span class="token string">"demo"</span><span class="token punctuation">)</span><span class="token punctuation">.</span>innerHTML <span class="token operator">=</span> <span class="token function">toCelsius</span><span class="token punctuation">(</span><span class="token number">77</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token operator">&lt;</span><span class="token operator">/</span>script<span class="token operator">&gt;</span>

<span class="token operator">&lt;</span><span class="token operator">/</span>body<span class="token operator">&gt;</span>
<span class="token operator">&lt;</span><span class="token operator">/</span>html<span class="token operator">&gt;</span>