Flash cards
Review the key moves
What is the main idea behind JavaScript Function Parameters?
Lesson checks
Practice each idea before moving on
Short Mimo-style checks built from this lesson's code, terms, and sequence.
Which statement best captures the main point of this lesson?
Complete the missing token from the example code.
___ multiply(a, b) {Put the learning moves in the order that makes the concept easiest to apply.
Parameters (Function Input)
Parameters allow you to pass (send) values to a function.
Parameters are listed inside the parentheses in the function definition .
Example
function multiply(a, b) {
return a * b;
}
let result = multiply(4, 5);Functions with One Parameter
A function can have one parameter.
Examples
function sayHello(name) {
return "Hello " + name;
}
let greeting = sayHello("John");Functions with Multiple Parameters
You can add as many parameters as you want, separated by commas.
Example
function fullName(firstName, lastName) {
return firstName + " " + lastName;
}
let name = fullName("John", "Doe");Parameters vs. Arguments
In JavaScript, function parameters and arguments are distinct concepts:
Parameters are the names listed in the function definition .
Arguments are the real values passed to, and received by the function .
Learn More
Function Arguments
Parameter Rules
JavaScript function definitions do not specify data types for parameters.
JavaScript functions do not perform type checking on the arguments.
JavaScript functions do not check the number of arguments received.
Incorrect Parameters
Accessing a function with an incorrect parameter can return an incorrect answer:
Example
function toCelsius(fahrenheit) {
return (5/9) * (fahrenheit-32);
}
let value = toCelsius();Default Parameter Values
ECMAScript 2015 allows function parameters to have default values.
The default value is used if no argument is provided.
Example
function myFunction(x, y = 10) {
return x + y;
}
myFunction(5);Function Return Values
- A function can return a value back to the code that called it
- The return statement is used to return a value from a function