In JavaScript, using functions involves two main steps: defining the function and then calling it. When you define a function, you’re essentially giving a name to a specific set of actions you want the computer to perform. To call a function, you simply type the function’s name followed by parentheses. This tells the computer to execute the actions associated with that function.
You’ve already been calling functions whenever you use commands that end with parentheses. The difference is that these functions were defined by someone else. Now, let’s explore how to define and call your own functions.
Imagine you have a toolbox with a tab labeled “functions.” Inside, you’ll find two blocks: one for defining a new function and another for calling a function. To define a function, drag out the new function block and give it a name. Then, add the code you want to execute when the function is called.
For example, you might add a command to set a fill color, a command to remove outlines, and a command to draw an ellipse at random X and Y positions. Once you’ve defined your function, the next step is to call it.
To call the function, drag out the block for calling functions and enter the name of your function. With both the definition and the call in place, your code will run as intended.
Defining a function gives a name to a block of code without executing it immediately. You can place the function definition anywhere in your program, but it’s often best to keep them organized at the end of your code. This helps maintain readability and structure.
When you call a function, the program runs the code inside the function and then returns to where it left off. This ability to define functions anywhere can make your code messy, so organizing them at the end is a good practice.
There’s a special function you’ve been defining but not explicitly calling in every program: the draw function. This function is unique because you define it, but the programming environment automatically calls it for you. By repeatedly calling the draw function, the environment can create smooth animations from still images.
Once you’ve written a function that works as intended, you can call it as often as needed without worrying about the details. This makes your code easier to understand and debug. By using a single name to reference a complex block of code, you simplify your program’s logic and make it easier to locate and fix any issues.
Now that you understand the basics, dive in and start experimenting with functions in your own projects!
Start by defining a simple function in JavaScript that performs a basic task, like displaying a message in the console. Then, practice calling your function multiple times in different parts of your code. This will help you understand how functions can be reused and how they affect the flow of your program.
Use the concept of functions to create a drawing tool. Define a function that draws a shape, such as a circle or square, at random positions on the canvas. Call this function multiple times to create a pattern or design. This activity will reinforce how functions can simplify repetitive tasks.
Write a small program with multiple functions, each performing a different task. Organize your functions at the end of your code, and call them in the main part of your program. This will help you practice organizing your code for better readability and maintenance.
Experiment with the draw function by creating a simple animation. Define the draw function to change the position or color of a shape over time. Observe how the programming environment automatically calls this function to create smooth animations.
Create a program with intentional errors in your function definitions or calls. Work with a partner to identify and fix these errors. This activity will enhance your debugging skills and deepen your understanding of how functions work in JavaScript.
Here’s a sanitized version of the provided YouTube transcript:
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There are two steps to using functions in JavaScript. First, we need to define our function. Then, we need to call it. When you define a new function, you’re simply giving a name to a defined set of actions you want the computer to perform. To call a function, you just type the name of the function followed by parentheses. This tells the computer to perform or execute the set of actions you named.
You have already been calling functions when you use commands that end with parentheses. The only difference is that someone else defined them for you.
Let’s walk through an example together. Notice that the toolbox now has a tab called functions. There are two blocks in there: one for defining a new function and one for calling a function. Drag a new function block out and type in the name you want to give the function. Now add the code you want to run when the function is called.
We’ll add a fill command to set the color, a no stroke command to remove the outline, and an ellipse command set to a random X and Y position.
Now that we have defined a function, we need to call it. To call the function, we drag out the other block in the functions tab and add the name of our function. Now that we have both defined and called our function, the code will actually run.
Defining a function simply gives a name to a block of code without actually running it. The definition can be written anywhere in your program. The rest of the code will run line by line just as before. Calling a function runs the lines of code inside the function. Afterwards, the program returns to where it left off when the function call was made.
The fact that function definitions can be placed anywhere means that your code can get messy and hard to read. We typically put function definitions at the end of our programs to help keep things organized.
You may have noticed that there’s one function you’ve been defining but not calling in every program you’ve written so far. The draw function is a special function that you, as the programmer, get to define, but that the environment takes care of calling for you. By calling the draw function repeatedly, the environment can create smooth animations from still images.
Once you have written a procedure or function that you know works as intended, you can call the function as often as you wish without worrying about the details or problems you had to solve to get it working. By referencing a large and complex block of code by a single name, it makes it much easier to understand what a program is doing by reading the code, and also easier to locate and fix problems or errors.
Let’s go ahead and dive in!
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This version removes informal language and maintains a professional tone while preserving the original content’s meaning.
Functions – A block of code designed to perform a specific task when called upon in a program. – Example sentence: In JavaScript, we use functions to organize our code and make it reusable.
Define – To specify the meaning or behavior of a function or variable in a program. – Example sentence: Before using a function, you must define it with a name and a set of instructions.
Call – To execute a function by using its name followed by parentheses in a program. – Example sentence: When you call a function, the computer runs the code inside it.
Code – A set of instructions written in a programming language that tells a computer what to do. – Example sentence: Writing clean code helps others understand your program better.
Program – A complete set of code that performs a specific task or set of tasks on a computer. – Example sentence: We created a program to calculate the average of test scores.
Organize – To arrange code in a structured and logical way to improve readability and efficiency. – Example sentence: Good programmers organize their code into functions and modules.
Draw – To create shapes or images on the screen using code. – Example sentence: Using JavaScript, you can draw graphics on a web page with the canvas element.
Actions – Specific tasks or operations that a program performs in response to user input or other events. – Example sentence: The program performs different actions based on the button the user clicks.
Computer – An electronic device that processes data according to a set of instructions called a program. – Example sentence: A computer can execute millions of instructions per second.
JavaScript – A programming language commonly used to create interactive effects within web browsers. – Example sentence: JavaScript is essential for adding dynamic content to websites.
