Order of default parameter values important to es6?
I hope to clarify something.
ES6 provides advanced parameter handling and allows you to pass default parameter values.
function f (x, y = 7, z = 42) {
return x + y + z
}
f(1) === 50
This works great. However, if I change the arguments to look like this: (x = 7, y, z = 42)
returns NaN
.
function f (x = 7, y, z = 42) {
return x + y + z
}
f(1) === 50
Can someone explain why this is happening?
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Order matters when you pass values to a function. In the first case, you only pass one variable to the function. This value will be assigned to the variable x
. Since you are only passing one variable, the rest of the values for other parameters are considered null. However, since you assigned default values for these parameters, the function will try to evaluate 1 + 7 + 52
, which resolves to 50.
In your second case, you are passing 1 as the value of the variable x
. Since the parameter y
remains unassigned, so the function will evaluate 1 + undefined + 42
which is the type NaN
.
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