使用递归达到嵌套数组项-javascript

Question

I'm trying to reach the center of a nested array using recursion. This is part of a larger problem I'm trying to solve. I'm sure the solution is somewhat elementary. I've been learning JS/web dev and am stumped.

Here's my code:

var j = [[[["hey!"]]]];

function getNested(obj) {
for (var i = 0; i < obj.length; i++) {
    if (Array.isArray(obj[i])) {
        obj = obj[i];
        getNested(obj);
    } 
    return obj[i];
  } 
}

The function is supposed to return the 'hey!' string, but I can't seem to get it right.

Answer 1

You are close, just switch out the findType(obj) for return getNested(obj[i]) . This will give you a recursive function that drills down into the array until the item in the array is not another array. Also, the for-loop was unnecessary, given your example input.

This will only work if your nested arrays have exactly one element. Others have expressed this in the comments.

var j = [[[["hey!"]]]];

function getNested(obj) {
    if (Array.isArray(obj)) {
        return getNested(obj[0]);
    } 
    return obj;
}

var str = getNested(j);
console.log(str); // "hey!"

jsFiddle Demo

Answer 2

There is no need for recursion, a simple while loop will already do the trick

var j = [[[["hey!"]]]];

function getNested(obj) {
    while (Array.isArray(obj)) { obj = obj[0]; } 
    return obj;
}

var str = getNested(j);
console.log(str); // "hey!"

The recursive implementation has the nice property that it is purely functional though if you rewrite it like so:

var j = [[[["hey!"]]]];

function getNested(obj) {
    return Array.isArray(obj)? getNested(obj[0]): obj;
}

var str = getNested(j);
console.log(str); // "hey!"

Still its performance would be worse though.