출처 (Original Post) : http://www.w3schools.com
Ending Statements With a Semicolon?
With traditional programming languages, like C++ and Java, each code statement has to end with a semicolon.
Note: The external script cannot contain the <script> tag!
To use the external script, point to the .js file in the “src” attribute of the <script> tag:
Note: Remember to place the script exactly where you normally would write the script!
A variable is a “container” for information you want to store. A variable’s value can change during the script. You can refer to a variable by name to see its value or to change its value.
Rules for variable names:
- Variable names are case sensitive
- They must begin with a letter or the underscore character
Declare a Variable
You can create a variable with the var statement:
var strname = some value
You can also create a variable without the var statement:
strname = some value
Assign a Value to a Variable
You can assign a value to a variable like this:
var strname = "Hege"
Or like this:
strname = "Hege"
The variable name is on the left side of the expression and the value you want to assign to the variable is on the right. Now the variable “strname” has the value “Hege”.
Lifetime of Variables
When you declare a variable within a function, the variable can only be accessed within that function. When you exit the function, the variable is destroyed. These variables are called local variables. You can have local variables with the same name in different functions, because each is recognized only by the function in which it is declared.
If you declare a variable outside a function, all the functions on your page can access it. The lifetime of these variables starts when they are declared, and ends when the page is closed.
A function named "myfunction" is not the same as "myFunction"
and a variable named "myVar" is not the same as "myvar".
capitalization closely when you create or call variables,
objects and functions.
your script to make it more readable. The following lines are
Break up a Code Line
You can break up a code line within a text string with
a backslash. The example below will be displayed properly:
However, you cannot break up a code line like this:
You can add comments to your script by using two slashes //:
//this is a comment
or by using /* and */ (this creates a multi-line comment
/* This is a comment