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- <!DOCTYPE html>
- <html>
- <head>
- <title>Page Title</title>
- </head>
- <body>
- <h3>Round up or down?</h3>
- <label for="round-up">
- <input type="radio" name="round" value="up" id="round-up">
- <span>Up</span>
- </label>
- <label for="round-down">
- <input type="radio" name="round" value="down" id="round-down" checked>
- <span>Down</span>
- </label>
- <div>
- <pre id='code'>
- <span class='p'>var</span> colorsArray = [
- <span class="r">"red"</span>,
- <span class="r">"orange"</span>,
- <span class="r">"yellow"</span>,
- <span class="r">"green"</span>,
- <span class="r">"blue"</span>,
- ];
- <span class='o'>// Generates a random decimal number between 0 and 1.</span>
- <span class='p'>var</span> randomNumber = Math.random();
- <span class='o'>// Multiply `randomNumber` by the array length to get</span>
- <span class='o'>// a random decimal number between 0 and "array length".</span>
- <span class='p'>var</span> unroundedArrayIndex = randomNumber * colorsArray.length;
- <span class='o'>// Since a decimal is not a valid array index,</span>
- <span class='o'>// round the random array index to a whole number.</span>
- <span class='p'>var</span> arrayIndex = Math.<span class='round-fn'>floor</span>(unroundedArrayIndex);
- colorsArray[arrayIndex];
- </pre>
- <pre>
- <span class="b random-number"></span>
- <span class="b random-number"></span> * <span class="b" id="array-length"></span> === <span class="b unrounded-array-index"></span>
- Math.<span class="round-fn"></span>(<span class="b unrounded-array-index"></span>) === <span class="b array-index"></span>
- colorsArray[<span class="b array-index"></span>] === <span id="index-value"></span>
- </pre>
- </div>
- <button id="refresh">Run it again</button>
- </body>
- </html>
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