Functions: Returning Values
Returning values
A function can return a value. Sometimes you just need a function to do something, like putting on your jacket. Other times, you want information sent back to you, so you can use it somewhere else, like calculating area.
To have information sent back to you, use the return keyword. This only works inside of functions. When the computer sees this in the function, it stops what it's doing and goes back to where it was when the function was called. It's sort of like it you had your jacket on halfway and someone yelled return (or stop!). You'd have half a jacket on.
If you just use return without a value, then you get back undefined.
If you don't use return at all, that's what a function normally returns (like in our putOnJacket()
example). Sometimes that's fine. However, you can send back any kind of variable you want, including a function.
Just include it after the return keyword.
- function getFavoriteNumber()
- {
- return 317;
- }
- getFavoriteNumber(); //317
Saving a returned value
If you're going to return a value, you usually want to save it to a variable and use it later. (There are exceptions.) This is easy! Just create a variable like normal with let and a name and then set it equal to the function call.
- let fav = getFavoriteNumber();
- fav; //317
Using a return value immediately
You can also use a return value inside a conditional check or some other function that needs its value.
- function checkWeather();
- {
- //it happens to be snowing as I write this, so...
- let weather = "snow";
- return weather;
- }
- if (checkWeather() === "snow")
- {
- alert("It's another snowy day!");
- }
This pops up an alert saying, "It's another snowy day!"
Assigning an existing function to a variable
It is also possible to assign a function to a variable. This is different than assigning a function call. This lets the new variable name act as if it's the original function.
- let gn = getFavoriteNumber;
- gn(); //317