The Summury

Table of Content

1. Function
2. Types of Functions
3. How to write a function
4. Control Flow

Function

Functions are one of the fundamental building blocks in JavaScript. A function in JavaScript is similar to a procedure—a set of statements that performs a task or calculates a value, but for a procedure to qualify as a function, it should take some input and return an output where there is some obvious relationship between the input and the output. To use a function, you must define it somewhere in the scope from which you wish to call it.

Types of Functions

we have two common types for function

• Decleration function:
  • It means that you will include the name of the function within the function itself
  • you can use the invoking before it whithout changing the code or having an error.
• Expression Function:
  • Its when you give the function to the spacific var “name”
  • it wont work if you put the invoking before.

How to write a Function

1. creat a function as this:

   Function Name( ) {code and the return if its important
   }

2. call or invoke the function

   by stating the name of your function followed by a paranrheses and semicollon name( );

Control Flow

The control flow is the order in which the computer executes statements in a script.

Code is run in order from the first line in the file to the last line, unless the computer runs across the (extremely frequent) structures that change the control flow, such as conditionals and loops.

A typical script in JavaScript or PHP (and the like) includes many control structures, including conditionals, loops and functions. Parts of a script may also be set to execute when events occur.

For example, the above excerpt might be inside a function that runs when the user clicks the Submit button for the form. The function could also include a loop, which iterates through all of the fields in the form, checking each one in turn. Looking back at the code in the if and else sections, the lines promptUser and submitForm could also be calls to other functions in the script. As you can see, control structures can dictate complex flows of processing even with only a few lines of code.

Control flow means that when you read a script, you must not only read from start to finish but also look at program structure and how it affects order of execution.