Learning PHP, MySQL, JavaScript, and CSS, 2nd Edition

Chapter 20 Answers

1. The O function returns an object by its ID, the S function returns the style property of an object, and the C function returns an array of all objects that access a given class.

2. You can modify a CSS attribute of an object using the setAttribute function, like this: myobject.setAttribute('font-size', '16pt'). You can also (usually) modify an attribute directly, using slightly modified property names where required, like this: myobject.fontSize = '16pt'. (Recall that JavaScript reserves the hyphen character for use as a mathematical operator, so when accessing a hyphenated CSS property you must omit the hyphen and set the character that followed it to uppercase.)

3. The properties that provide the width and height available in a browser window are window.innerHeight and window.innerWidth.

4. To make something happen when the mouse pointer passes over and out of an object, attach the code that does this to the onmouseover and onmouseout events.

5. To create a new element, implement code such as elem = document.createElement('span'), and to add the new element to the DOM, use code such as document.body.appendChild(elem).

6. To make an element invisible, set its visibility property to 'hidden' (use 'visible' to restore it again). To collapse an element’s dimensions to zero, set its display property to 'none' (use 'block' to restore it).

7. To set a single event at a future time, call the setTimeout function, passing it the code or function name to execute and the time delay in milliseconds. ...