This is one of those job interview tests on HackerRank that I am embarrassed to say I didn't complete within the allotted 20 minutes, and it's driving me nuts. Basically, you're given the following:
function myList() {
// write code here
}
function main() {
// You can't edit this function. This is just pseudo, from what I can remember
const obj = myList();
if (operation === "add")
obj.add(item);
else if (operation === "remove")
obj.remove(item);
else
obj.getList();
// Some more stuff here
}
So my first train of thought was to write the following inside myList():
let objList = [];
function add(item) {
objList.add(item)
}
// etc., etc.
return {add, remove, getList};
Needless to say, the above didn't work, with the error: obj.add is not a function, in the main function.
I tried experimenting with this and the returns (only returning add, with or without {}), but didn't really get anywhere. What could I have done to get this working?
For obj, inside myList() you could have run a closure, that is a self invoking function returning, in this case, an object with your k:v exports, but with private access to the context of the now expired anonymous caller. With "const add = function" etc statements you can define values for your exports, while the objList goes in the private context.
As the answer from Attersson already suggested, you could use a closure inside the myList function. This would allow to only expose the three methods add, remove and getList while the original list cannot be accessed. Here is an example:
function myList() {
return (() => {
const obj = {itemList: []}
const add = (item) => obj.itemList.push(item)
const remove = (item) => obj.itemList = obj.itemList.filter(i => i !== item)
const getList = () => obj.itemList
return {add, remove, getList}
})()
}