In this short article, you will learn how to exit a JavaScript function.
When creating a function using JavaScript, you may want to stop its execution and exit it. To do so, these are two ways of doing it:
return
statement. Once your program reaches this instruction, it will exit the function by returning a value.Before discovering how to exit in JavaScript, let's see when a function exits by itself.
Here is an example:
function writeMyName(name) {
// Print the name variable
console.log(name)
// Then, reach the end of the function
// and automatically exit it
}
writeMyName('Gaël')
// Output: "Gaël"
In the case above, you have a simple example. As you can see, the function only prints the name
variable. In that case, the program exit the function after executing all the instructions.
Now, let's dig a bit further and see how you can exit a function using the return
statement.
This statement allows you to leave a function once you reach it.
Let me show you an example:
function writeMyName(name) {
// Execute the return instruction
// and automatically exit the function
// Note: all code after a `return` isn't executed
return
// Print the name variable
console.log(name)
}
writeMyName('Gaël')
// No output
By default, the return
statement send an undefined value. As an example, if you save the writeMyName
output to a variable and print it, here what you will get:
function writeMyName(name) {
// Execute the return instruction
// and automatically exit the function
// Note: all code after a `return` isn't executed
return // No value = undefined
// Print the name variable
console.log(name)
}
const output = writeMyName('Gaël')
console.log(output)
// Output: undefined
Now, you know how to stop a function and exit it whenever you want. But, let's imagine that you want to exit a JavaScript process and send a result value.
You can do the same as we did before, but specify a value. This value can come from a variable.
function writeMyName(name) {
if (name === 'Wrong') return false
// Print the name variable
console.log(name)
return true
}
console.log(writeMyName('Gaël'))
// Output:
// "Gaël"
// true
console.log(writeMyName('Wrong'))
// Output: false
In the example above, you're first checking the name
variable value. If the value is "Wrong", you exit the function and send a false
boolean value.
Otherwise, you print the name
variable, then send a true
boolean value as a return value.
That's all about how you can exit a JavaScript function. 🚀