CODEWITHSUNDEEP
javascriptarraysloops
coure2011
coure2011

Reputation: 42454

looping through arrays of arrays

I have an arrays of arrays (some thing like graph), How to iterate all arrays?

var parentArray = [
 [[1,2,3],[4,5,6],[7,8,9]],
 [[10,11,12],[13,14,15],[16,17,18]],
 [[19,20,21],[22,23,24],[26,27,28]]
];

Its just an example array, actual can contains any number of array and then arrays. How to print all those numbers? Its similar to html objects DOM

Upvotes: 22

Views: 98717

Answers (11)

N Djel Okoye
N Djel Okoye

Reputation: 1078

const parentArray = [
  [
    [1,2,3],
    [4,5,6],
    [7,8,9]
  ],
  [
    [10,11,12],
    [13,14,15],
    [16,17,18]
  ],
  [
    [19,20,21],
    [22,23,24],
    [26,27,28]
  ]
]

parentArray.map(
  childArray => childArray.map(
    grandChildArray => grandChildArray.map(
      arrayItem => console.log(arrayItem)
    )
  )
)

Upvotes: 0

Tendai kastande
Tendai kastande

Reputation: 41

How to loop an indefinite nested array in JavaScript:

function isArray(x) {
  return typeof x === "object";
}

let x = [1, 2, 3, 4, 5, [5, [2, 3, 4], 3], [[[0]]]];

function loop_map(x, idx) {
  x.map((res, i) => {
    console.log("Index ", i);
    if (isArray(res)) {
      loop_map(res, i);
    } else {
      console.log(res);
    }
  });
}

loop_map(x, 0);

Upvotes: 0

Kasey
Kasey

Reputation: 11

I don't know if this is new or what, but it may please you to know that there is an Array prototype ".flat" that can be used here to make the array one-dimensional:

var parentArray = [
 [[1,2,3],[4,5,6],[7,8,9]],
 [[10,11,12],[13,14,15],[16,17,18]],
 [[19,20,21],[22,23,24],[26,27,28]]
];

function flatten(){
flatArray = parentArray.flat(Infinity);
flatArray.forEach(function(item, i){
  console.log(item)
})
}

Upvotes: 1

Anil_M
Anil_M

Reputation: 11453

Using array.forEach method 

parentArray.forEach( function(childArray) {
  childArray.forEach(function(item){
  console.log(item);
  });
 });

[ 1, 2, 3 ]
[ 4, 5, 6 ]
[ 7, 8, 9 ]
[ 10, 11, 12 ]
[ 13, 14, 15 ]
[ 16, 17, 18 ]
[ 19, 20, 21 ]
[ 22, 23, 24 ]
[ 26, 27, 28 ]

One liner using => "fat arrow" in ES6+

parentArray.forEach(subarray => { subarray.forEach( item => {console.log(item); }); });


[ 1, 2, 3 ]
[ 4, 5, 6 ]
[ 7, 8, 9 ]
[ 10, 11, 12 ]
[ 13, 14, 15 ]
[ 16, 17, 18 ]
[ 19, 20, 21 ]
[ 22, 23, 24 ]
[ 26, 27, 28 ]

If you want to list individual number in item, add another layer of forEach.

Upvotes: 6

Shane van Wyk
Shane van Wyk

Reputation: 1900

what you need to do is something like this

var parentArray = [
 [[1,2,3],[4,5,6],[7,8,9]],
 [[10,11,12],[13,14,15],[16,17,18]],
 [[19,20,21],[22,23,24],[26,27,28]]
];

for(int i = 0; i < parentArray.length;i++){
   var value = parent[i];

   for(int j = 0; j < parent[i].length; j++){
      var innerValue = parent[i][j];
   }
}

So this will be like a nested loop, then there where innerValue and value is you can do some operations, hope it helps

Upvotes: 11

Saul
Saul

Reputation: 18041

One option would be to use recursion which works with any number of dephts. See traverse(), it's not tested but should give a rough idea:

String.prototype.lpad = function(padString, length) {
    var str = this;
    while (str.length < length)
        str = padString + str;
    return str;
}

var level = 0;

function traverse(obj) {
   if (obj instanceof Array) { level++; for(var i in obj) traverse(obj[i]); level--; }
   else console.log(''.lpad('-', level) + obj);
}

Upvotes: 5

zhangsn
zhangsn

Reputation: 59

if you just want to print all the members,how about this?

var items = parentArray.toString().split(",");
for(var i=0,j=items.length;i<j;i++)
    console.log(items[i]);

Upvotes: 5

laurent
laurent

Reputation: 90776

If you have a DOM like structure, you need to recursively iterate through the elements. Something like that should work:

function printArray(array) {
    for (var i = 0; i < array.length; i++) {
        var v = array[i];
        if (v instanceof Array) {
            printArray(v);
        } else {
            console.log(v);
        }
    }
}

Upvotes: 2

Sascha Galley
Sascha Galley

Reputation: 16091

This recursive function should do the trick with any number of dimensions:

var printArray = function(arr) {
    if ( typeof(arr) == "object") {
        for (var i = 0; i < arr.length; i++) {
            printArray(arr[i]);
        }
    }
    else document.write(arr);
}

printArray(parentArray);

Upvotes: 23

yoozer8
yoozer8

Reputation: 7489

You would use nested for loops here. The outer loop would iterate the parent array, giving you one of the internal arrays each time. The inner loop would give you the items within each array. Example:

for(childArray in parentArray){
    for(item in childArray){
        //do stuff here to each number
    }
}

Upvotes: 0

Van Coding
Van Coding

Reputation: 24534

For 2 dimenional Arrays:

for(var i = 0; i < parentArray.length; i++){
    for(var j = 0; j < parentArray[i].length; j++){

        console.log(parentArray[i][j]);
    }
}

For arrays with an unknown number of dimensions you have to use recursion:

function printArray(arr){
    for(var i = 0; i < arr.length; i++){
        if(arr[i] instanceof Array){
            printArray(arr[i]);
        }else{
            console.log(arr[i]);
        }
    }
}

Upvotes: 18

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