JavaScript Function Return
Returning Values from Functions
A function can return a value back to the code that called it.
The return statement is used to send a value out of a function.
The return Statement
When JavaScript reaches a return statement, the function stops executing.
The value after return is sent back to the caller.
Example
function sayHello() {
return "Hello World";
}
let message = sayHello();
The variable message now contains the returned value.
Returning a Calculated Value
Most functions return the result of a calculation or operation.
Example
function multiply(a, b) {
return a * b;
}
let result = multiply(4, 5);
The returned value can be used anywhere a value is expected.
Using Returned Values in Expressions
You can use a function call inside another expression.
Example
function add(a, b) {
return a + b;
}
let total = add(2, 3) * 10;
Returning Text or Numbers
A function can return any type of value, such as text or numbers.
Example
function fullName(firstName, lastName) {
return firstName + " " + lastName;
}
fullName("John", "Doe");
Returning from a Function Stops Execution
Code written after return will not be executed.
Example
function testReturn() {
return "Done";
console.log("This will never run");
}
Functions Without return
If a function does not return a value, it returns undefined.
Example
function noReturn() {
let x = 10;
}
let result = noReturn();
The value of result is undefined.
Returning Values Early
You can use return to stop a function early, based on a condition.
Example
function checkAge(age) {
if (age < 18) {
return "Too young";
}
return "Access granted";
}
Try it Yourself »
Returning Values to HTML
Returned function values are often used to update HTML content.
Example
<p id="demo"></p>
<script>
function toCelsius(farenheit) {
return (5 / 9) * (farenheit - 32);
}
document.getElementById("demo").innerHTML = toCelsius(77);
</script>
Try it Yourself »
Common Mistakes
Forgetting return
A function without return sends back undefined.Expecting code after return to run
Code after return is ignored.Confusing console.log() with return
console.log() shows output but does not return a value.
Next Chapter
Next: Function Declarations and Function Expressions
