how to create use functions javascript essentials

certainly! functions are one of the fundamental building blocks in javascript. they allow you to encapsulate code for reuse, making your code more modular and easier to read. in this tutorial, we'll cover the essentials of creating and using functions in javascript, along with code examples to illustrate each point.

1. **defining a function**

in javascript, you can define a function using the `function` keyword followed by a name, parentheses, and curly braces. here's the basic syntax:

example:

2. **calling a function**

once a function is defined, you can call it by using its name followed by parentheses. if the function takes parameters, you provide them inside the parentheses.

example:

3. **function parameters and arguments**

functions can take parameters, which are variables used to pass information into the function. when you call a function, you provide arguments that correspond to these parameters.

example:

4. **returning values**

functions can return values using the `return` statement. this allows you to send a value back to the caller.

example:

5. **function expressions**

you can also create functions as expressions, which can be anonymous (without a name) and assigned to variables.

example:

6. **arrow functions**

introduced in es6, arrow functions provide a shorthand syntax for writing function expressions. they also do not have their own `this`, which is important in certain contexts.

example:

7. **default parameters**

you can define default values for parameters in case no arguments are provided during the function call.

example:

8. **rest parameters**

rest parameters allow you to pass an arbitrary number of arguments to a function. these are represented by three dots (`...`) before the parameter name.

example:

9. **anonymous functions and callbacks**

functions can be passed as arguments to other functions. these are often referred to as callback functions.

example:

10. **iife (immediatel ...

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function expressions
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