I'm trying to create a map function that supports computing nested arrays, using recursion:
This function, when a unidimesional (eg. [1,2,3,4] ) array is used works fine:
const map = (oldArray, callback, newArray = []) => {
//base case: check if there are any items left in the original array to process
if (oldArray.length <= 0){
//if all items have been processed return the new array
return newArray
} else {
//destructure the first item from old array and put remaining in a separate array
const [item, ...theRest] = oldArray
// create an array of the current new array and the result of the current item and the callback function
const interimArray = [...newArray, callback(item)]
// return a recursive call to to map to process the next item.
return map(theRest, callback, interimArray)
}
}
But, I want to support a nested array, so for example, I have an array like this:
const array = [1,[1,2],3]
and I want to apply a function, eg: (x)=>x+1;
I have this implementation so far, but I can't wrap my mind around it.
function rnMap(oldArr, fn, newArr = []) {
const [item, ...rest] = oldArr;
if (oldArr.length <= 0) {
return newArr;
} else if (Array.isArray(item)) {
return rnMap(item, fn, [...newArr, rnMap(item, fn, [])]);
} else {
const interimArray = [...newArr, fn(item)];
return rnMap(rest, fn, interimArray);
}
}
const rnRes = rnMap(nArr, (e) => {
return e + 1;
});
console.log(rnRes);
It returns [ 2, [ 2, 2 ], 2, 2 ] but it suppose to return [2,[2,3],4]
If anyone could help me will be appretiated. Thanks in advance.
No loop approach, sort of ...
const
map = ([value, ...array], fn) => {
if (value === undefined) return [];
return [
(Array.isArray(value) ? map(value, fn) : fn(value)),
...map(array, fn)
];
},
array = [1, [1, 2], 3],
fn = x => x + 1;
console.log(map(array, fn));This would probably be the simplest solution.
// @ts-ignore
const func = (list: Array<any>) => {
return list.map(i => {
if (i instanceof Array) {
return func(i)
}
return i+1
})
}
const result = func([1,[1,2],3])
console.log('log result', result)
This is in typescript, let me know if you want a js version
Finally I found the error, here is my solution:
function rnMap(oldArr, fn, newArr = []) {
const [item, ...rest] = oldArr;
if (oldArr.length <= 0) {
return newArr;
} else if (Array.isArray(item)) {
return rnMap(rest, fn, [...newArr, rnMap(item, fn, [])]);
} else {
return rnMap(rest, fn, [...newArr, fn(item)]);
}
}
const rnRes = rnMap([1, 2, [3, 4, [5, 6]], 7], (e) => {
return e + 1;
});
console.log(rnRes);