Finding objects in a nested array along with their position

Question

I've taken the following sample from a different question. And I am able to identify the object. But I also need to find our the position of that object. For example:

var arr = [{
    Id: 1,
    Categories: [{
        Id: 1
      },
      {
        Id: 2
      },
    ]

  },
  {
    Id: 2,
    Categories: [{
        Id: 100
      },
      {
        Id: 200
      },
    ]

  }
]

If I want to find the object by the Id of the Categories, I can use the following:

var matches = [];
var needle = 100; // what to look for

arr.forEach(function(e) {
    matches = matches.concat(e.Categories.filter(function(c) {
        return (c.Id === needle);
    }));
});

However, I also need to know the position of the object in the array. For example, if we are looking for object with Id = 100, then the above code will find the object, but how do I find that it's the second object in the main array, and the first object in the Categories array?

Thanks!

Exactly what sort of output are you looking for? Something like { idIndex: 1, catIndex: 0 } or what? — CertainPerformance
– CertainPerformance, Commented Oct 12, 2018 at 6:14
I am looking for arrIndex: 0. So basically I need to know that it's position is 1 in main array, and that within category, it's at position 0. — asanas
– asanas, Commented Oct 12, 2018 at 6:15

Ahorn · Accepted Answer · 2018-10-12 06:33:49Z

3

Well, if every object is unique (only in one of the categories), you can simply iterate over everything.

var arr = [{
    Id: 1,
    Categories: [{Id: 1},{Id: 2}]
  },
  {
    Id: 2,
    Categories: [{Id: 100},{Id: 200}]
  }
];

var needle = 100;

var i = 0;
var j = 0;

arr.forEach(function(c) {
  c.Categories.forEach(function(e) {
    if(e.Id === needle) {
      console.log("Entry is in position " + i + " of the categories and in position " + j + " in its category.");
    }
    j++;
  });
  j = 0;
  i++;
});

edited Oct 12, 2018 at 6:33

answered Oct 12, 2018 at 6:26

Ahorn

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Comments

mtizziani · Accepted Answer · 2018-10-12 06:20:23Z

0

function findInArray(needle /*object*/, haystack /*array of object*/){
  let out = [];
  for(let i = 0; i < haystack.lenght; i++) {
    if(haystack[i].property == needle.property) {
      out = {pos: i, obj: haystack[i]};
    }
  }
  return out;
}

if you need the position and have to filter over an property of the object you can use a simple for loop. in this sample your result is an array of new object because there can be more mathches than 1 on the value of the property.

i hope it helps

answered Oct 12, 2018 at 6:20

mtizziani

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Comments

Saurabh Yadav · Accepted Answer · 2018-10-12 06:26:52Z

Iterate over the array and set index in object where match found

var categoryGroups = [{
        Id : 1,
        Categories : [{
                Id : 1
            }, {
                Id : 2
            },
        ]

    }, {
        Id : 2,
        Categories : [{
                Id : 100
            }, {
                Id : 200
            },
        ]

    }
]

var filterVal = [];
var needle = 100;
for (var i = 0; i < categoryGroups.length; i++) {

    var subCategory = categoryGroups[i]['Categories'];
    for (var j = 0; j < subCategory.length; j++) {

        if (subCategory[j]['Id'] == findId) {
            filterVal.push({
                catIndex : i,
                subCatIndex : j,
                id : needle
            });
        }

    }
}

console.log(filterVal);

Akrion · Accepted Answer · 2018-10-12 06:56:56Z

0

Here is solution using reduce:

var arr = [{ Id: 1, Categories: [{ Id: 1 }, { Id: 2 }, ] }, { Id: 2, Categories: [{ Id: 100 }, { Id: 200 }, ] } ]

const findPositions = (id) => arr.reduce((r,c,i) => { 
   let indx = c.Categories.findIndex(({Id}) => Id == id) 
   return indx >=0 ? {mainIndex: i, categoryIndex: indx} : r
}, {})

console.log(findPositions(100))  // {mainIndex: 1, categoryIndex: 0}
console.log(findPositions(1))    // {mainIndex: 0, categoryIndex: 0}
console.log(findPositions(200))  // {mainIndex: 1, categoryIndex: 1}
console.log(findPositions(0))    // {}

edited Oct 12, 2018 at 6:56

answered Oct 12, 2018 at 6:26

Akrion

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Comments

Nina Scholz · Accepted Answer · 2018-10-12 07:13:35Z

0

Beside the given answers with fixt depth searh, you could take an recursive approach by checking the Categories property for nested structures.

function getPath(array, target) {
    var path;
    array.some(({ Id, Categories = [] }) => {
        var temp;
        if (Id === target) {
            path = [Id];
            return true;
        }
        temp = getPath(Categories, target);
        if (temp) {
            path = [Id, ...temp];
            return true;
        }
    });
    return path;
}

var array = [{ Id: 1, Categories: [{ Id: 1 }, { Id: 2 },] }, { Id: 2, Categories: [{ Id: 100 }, { Id: 200 }] }];

console.log(getPath(array, 100));

.as-console-wrapper { max-height: 100% !important; top: 0; }

answered Oct 12, 2018 at 7:13

Nina Scholz

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