Get array's depth in JavaScript

问题:

In order to get the array's depth I thought I can use the flat() method like so:

function getArrayDepth(ry){
  // number of levels: how deep is the array
  let levels = 1;
  // previous length
  let prev_length = 1;
  // current length
  let curr_length = ry.length;
  //if the resulting array is longer than the previous one  add a new level
  while(curr_length > prev_length){
  ry = ry.flat();
  prev_length = curr_length
  curr_length = ry.length;
  levels ++
  }
  return levels;
}



let testRy = [1,2,[3,4,[5,6],7,[8,[9,91]],10],11,12]

console.log(testRy);

console.log(getArrayDepth(testRy))

console.log(testRy);

It seams it works BUT if one of the arrays inside has a length of 1

let testRy = [1, 2, [3, 4, [5, 6], 7, [8, [9] ], 10], 11, 12]

the function fails since the flattened array is as long as the previous one.

Is there a better way to get the depth of an array in javascript?

回答1:

I think a recursive approach is simpler. If your current item is an Array determine the max depth of its children and add 1.

function getArrayDepth(value) {
  return Array.isArray(value) ? 
    1 + Math.max(...value.map(getArrayDepth)) :
    0;
}



let testRy = [1,2,[3,4,[5,6],7,[8,[9,91]],10],11,12]

console.log(testRy);

console.log(getArrayDepth(testRy))

console.log(testRy);

回答2:

You can use a recursive function:

function getArrayDepth(obj) {
    if (Array.isArray(obj)) return 1 + Math.max(...obj.map(t => getArrayDepth(t)))
    else return 0
}


console.log(getArrayDepth([1,2,[3,4,[5,6],7,[8,[9,91]],10],11,12]))
console.log(getArrayDepth([1,[1]]))

回答3:

function test(arr) {
  return 1 + (arr instanceof Array ? arr.reduce(function(max, item) {
    return Math.max(max, test(item));
  }, 0) : -1);
}



let testRy = [1,2,[3,4,[5,6],7,[8,[9,91]],10],11,12];

console.log(test(testRy));
console.log(test([]));

回答4:

This one is a bit easier to understand, if you'd like.

var array = [
[0, 1],
[1, 2, 3, [1, 0]],
[2, 3, [1, 2, [5]]],
[1, [6, 3, [1, 2, [1, 0]]]],
[2]
]

function depth(array, rec) {
if (!Array.isArray(array)) throw new Exception('not an array');

var res = rec;
for(var i = 0; i < array.length; ++i) {
    if (Array.isArray(array[i])) {
    var subDepth = depth(array[i], rec + 1);
    if (subDepth > res) {
        res = subDepth;
    }
  }
}
return res;
}

回答5:

Convert the array to string lets assume We are given a string having parenthesis like below “( ((X)) (((Y))) )” We need to find the maximum depth of string, like 4 in above example. Since ‘Y’ is surrounded by 4 balanced parenthesis.

Take two variables max and current_max, initialize both of them as 0. Traverse the string, do following for every character a) If current character is ‘(’, increment current_max and update max value if required. b) If character is ‘)’ means we previously had a ‘(’ character so decrement current_max without worry but dont reduce max value .

If current_max is greater than max then update max value to current_max at that instance. after traverse is completed the max is is the depth of the array.