We always have to validate if the arguments passed in a function have a value or they are undefined
but, do we really?
Introduction
In my last post, I talked about Destructuring Assignment In A Function Parameter and why it is handy when you have optional parameters in a function and don't want to pass undefined
or null
.
With that been said, what if you have a function where all the parameters are required? Again, since ES2015 (aka ES6) this can be easily implemented. Let's dive in.
Use Case
If you take a Tip Calculator project as an example, you probably will need always the same parameters:
- Bill Amount.
- Number of People.
- Service Quality.
The function you'll need would look like this 👇
function calculateTip(totalBill, numOfPeople, serviceQuality) {
// Your validation here
// Your code here
}
console.log(calculateTip(50, 2 , 0.2))
// 5.00
Inside the function, you'll have to do all the calculations AND all the validation; plus, most of the time I go with the same friend (2 people) and leave the standard tip (20%).
In this case, the only parameter that will be changing all the time will be the bill amount.
So, let's give numOfPeople
and serviceQuality
a default parameter:
function calculateTip(totalBill, numOfPeople = 2, serviceQuality = 0.2) {
// Your code here
}
console.log(calculateTip(50))
// 5.00
console.log(calculateTip(75))
// 7.50
Now, just when someone else is joining, or we want to leave a different tip percentage, it will be necessary to pass the rest of the arguments.
Conclusion
You don't really need to check if the argument in a function is undefined
, you can create a default value for it.
When a different value is provided, the default value will be overwritten.
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