HTML and CSS Reference
In-Depth Information
4. Save the example10-6.js file.
5. Now create a new HTML file called example10-6.html .
6. Copy the following HTML code into this file.
<!DOCTYPE html>
<meta charset="utf-8">
<title>Event Listeners</title>
<button id="btn">Click me!</button>
<script src="example10-6.js"></script>
7. Save this file.
Now open up the example10-6.html file in your web browser. If you click the button you should be confronted
by an alert dialog that contains the text Boo!
Making Decisions
When writing programs, you will meet scenarios in which you need to make a decision before executing code.
Maybe you want to check that the user has provided valid data, or that a number is within a certain range. You can
make these decisions in your code using if and else statements.
An if statement should contain a condition that evaluates to either true or false . If the condition evaluates to
true , the code within the block is executed; if it is false , the code is skipped. Here is an example of a simple if
if(a < b) {
document.write(“a is smaller than b!");
In this example, the condition would evaluate to true if the value of the a variable is smaller than the value of the b
variable. This means that the code would execute and the text would be output to the screen.
You can find a comprehensive list of JavaScript operators that can be used in conditions at
sions_and_Operators#Comparison_operators .
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