Reputation: 1180
I have the following code:
const ships = (length) => {
isSunk = false
console.log('BEFORE: ' + isSunk)
const shipSize = length
let hits = []
const hitLocation = location => {
hits.push(location);
isSunk = true;
console.log('INSIDE: ' + isSunk)
}
console.log('AFTER: ' + isSunk)
return {
isSunk,
hitLocation,
hits,
shipSize
}
}
const two = ships(2)
two.hitLocation(1)
two.hitLocation(2)
console.log('FINAL: ' + two.isSunk)
console.log('HITS: ' + two.hits)
Is there a reason why isSunk
is not saved as true
when I call it in the end?
Is it due to the nested functions?
Upvotes: 0
Views: 849
Reputation: 9198
The reason this happens is that isSunk
is just a local variable and a value in contrast to hits
which is also a local variable but an array and thus just a reference not a value.
As you return the object when calling ship()
these values and the reference get returned in an object.
Now when you call hitLocation()
it uses the local variable hits
to add an entry to the array and as the array is just a reference the local variable hits
and the hits
in the two
object have the same reference so they point to the same memory location, thus the update can be seen using the returned object.
On the other hand hitLocation()
also modifies the local variable isSunk
but as you do not return that and it is not a reference the object stored in variable two
is not updated.
The best way to fix this to my mind is using a class instead of a object here. This will be much more concise and clear than returning and/or passing the object you want to perform some action on to a function all the time.
Upvotes: 1
Reputation: 207531
When you set the boolean into the object, it is that value. It is not a reference to the variable. So when you change the variable, the value you saved inside of the object that you returned is not updated.
You can use a function to get the value
const ships = (length) => {
isSunk = false
console.log('BEFORE: ' + isSunk)
const shipSize = length
let hits = []
const hitLocation = location => {
hits.push(location);
isSunk = true;
console.log('INSIDE: ' + isSunk)
}
console.log('AFTER: ' + isSunk)
return {
isSunk: () => isSunk,
hitLocation,
hits,
shipSize
}
}
const two = ships(2)
two.hitLocation(1)
two.hitLocation(2)
console.log('FINAL: ' + two.isSunk())
Other option is to use a class.
class Ship {
hits = [];
constructor(length) {
this.shipSize = length;
}
get isSunk() {
return this.hits.length === this.shipSize;
}
hitLocation (location) {
this.hits.push(location);
console.log('INSIDE: ' + this.isSunk)
}
}
const two = new Ship(2)
two.hitLocation(1)
two.hitLocation(2)
console.log('FINAL: ' + two.isSunk)
Upvotes: 2