JavaScript Function Syntax
A JavaScript function is defined with the function keyword, followed by a name, followed by parentheses ().
Function names can contain letters, digits, underscores, and dollar signs (same rules as variables).
The parentheses may include parameter names separated by commas:
(parameter1, parameter2, …)
The code to be executed, by the function, is placed inside curly brackets: {}
Function Invocation
The code inside the function will execute when “something” invokes (calls) the function:
When an event occurs (when a user clicks a button)
When it is invoked (called) from JavaScript code
Automatically (self invoked)
You will learn a lot more about function invocation later in this tutorial.
Function Return
When JavaScript reaches a return statement, the function will stop executing.
If the function was invoked from a statement, JavaScript will “return” to execute the code after the invoking statement.
Functions often compute a return value. The return value is “returned” back to the “caller”:
Here is a simple scripts to perform a calculation and return the desirable result
This example calls a function which performs a calculation, and returns the result:
Returned result:
This example calls a function which performs a calculation, and returns the result:
12
Example 2:JavaScript Numbers
JavaScript numbers can be written with, or without decimals and
extra large or extra small numbers can be written with scientific (exponent) notation:
See results
34
34
12300000
0.00123
Example 3: Convert Fahrenheit to Celsius
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