JavaScript Functions — Parameters and Arguments

Learn what parameters, arguments, and return statements are with videos and animations.

Let’s understand what is a JavaScript Parameter& Argument.
Also what the return statement is.

In the previous article, we learned about the general idea of a function, function definition & function invocation. Visit to refresh your knowledge, if you want.

Let’s get a little more advanced with functions.

Table of Content:

1. JavaScript variables in functions
2. JavaScript Functions — Parameters & Arguments
3. JavaScript return statement

JavaScript variables in functions

JavaScript functions can also contain variables.
Let’s create a function called addNumbers() to demonstrate.

function addNumbers() {
const a = 5;
const b = 10;
const sum = a + b; // 5 + 10
return sum;
}
console.log(addNumbers());

Code Explanation:

In the function block {}, we have 3 variables a, b, and sum, with values.

In the end, we have the return keyword.

Followed by function call, addNumbers()

Logging the function call, to see the result inside the console.

But we can change the above code, using Parameters and Arguments to replace variable declaration & assignment.

JavaScript Functions — Parameters & Arguments

JavaScript function parameters are the names (placeholders) for values.

JavaScript function arguments are the actual values of parameters.

Let me explain it to you like we are having a street conversation or talk in an informal language as friends.

1. Parameters are variable names. The word parameter is just a fancy word for saying “variable name” in JS
2. Arguments are the actual values of those variables. The word argument is just another fancy word for saying “variable value”
3. So we use parameters(variable names) to refer to arguments(actual variable values)

Makes sense? Let’s see it in code, or better convert the above function’s variables & their values to parameters & arguments.

function addNumbers(a, b) {
const sum = a + b; // 5 + 10
return sum;
}
console.log(addNumbers(5, 10));

Code Explanation:

Instead of writing variable names inside the function block {}.

We wrote them inside the function parentheses().

And we gave arguments (actual variable values) on function call addNumbers(5, 10).

Most people can’t see the relationship between parameters & arguments (including myself). So I decided to make a video, animations, and pictures to help you visualize.

Notice, we don’t need to use a JavaScript keyword const , let or var to declare the variables a and b, inside the () parentheses.

JavaScript return statement

The JavaScript return statement as it sounds, it returns something.

When the JavaScript function reaches the return statement, it will stop the function execution and returns the value to the caller.

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