JavaScript Tutorial For Beginners - 13 | JavaScript Functions |JavaScript Local and Global Variable

JavaScript, JavaScript Functions, JavaScript local and Global variables Today in this tutorial we discuss on the topic is: JavaScript Functions: A JavaScript function is a block of code designed to perform a particular task. A JavaScript function is executed when "something" invokes it (calls it). 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 parameters are listed inside the parentheses () in the function definition.  Function arguments are the values received by the function when it is invoked.  Inside the function, the arguments (the parameters) behave as local variables. 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) 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": Why Functions: You can reuse code: Define the code once, and use it many times. You can use the same code many times with different arguments, to produce different results. Local Variables:  Variables declared within a JavaScript function, become LOCAL to the function.  Local variables can only be accessed from within the function. Since local variables are only recognized inside their functions, variables with the same name can be used in different functions.  Local variables are created when a function starts, and deleted when the function is completed.

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