Choosing an element from an array in JavaScript that meets a certain criteria

Question

Choosing an element from an array in JavaScript that meets a certain criteria

How can I isolate an object from an array where the value for the "slug" key is "A"?

For instance, consider the following data:

 var allItems = [
    {
        "slug": "henk",
        "company_founded": "2008",
        "company_category": "Clean",
        "company_logo": false,
        "company_description": "",
    }
    {
        "id": "bas",
        "company_founded": "2012",
        "company_category": "Health",
        "company_logo": false,
        "company_description": "",
    }
    {
        "slug": "jan",
        "company_founded": "2005",
        "company_category": "Clean",
        "company_logo": false,
        "company_description": "",
    }
]

I aim to store the object with the slug value of "henk" in a new variable.

Thus, after extraction, I will be able to work with something similar to this:

var = SelectedItem = {
    "slug": "henk",
    "company_founded": "2012",
    "company_category": "Health",
    "company_logo": false,
    "company_description": "",
}

Appreciate your help!

javascript arrays json object

Answer 1

Answer №1

To find the specific element you are looking for, iterate through your list and use a condition to select it:

let result;
for(const item of allItems) {
    if(item.company_founded === "2012") {
        result = item;
        break;
    }
}

Answer 2

To find the specific element you are looking for, iterate through your list and use a condition to select it:

let result;
for(const item of allItems) {
    if(item.company_founded === "2012") {
        result = item;
        break;
    }
}

Answer 3

Answer №2

If you're interested, I recommend checking out the documentation on Array.prototype.find:

 const targetItem = itemList.find(function(item){
     return item.slug === 'henk';
 });

Answer 4

If you're interested, I recommend checking out the documentation on Array.prototype.find:

 const targetItem = itemList.find(function(item){
     return item.slug === 'henk';
 });

Answer 5

Answer №3

If you have a scrambled object, one approach is to loop through all properties and filter out the objects that contain a specific value.

var allItems = [{ "slug": "henk", "company_founded": "2008", "company_category": "Clean", "company_logo": false, "company_description": "", }, { "id": "bas", "company_founded": "2012", "company_category": "Health", "company_logo": false, "company_description": "", }, { "slug": "jan", "company_founded": "2005", "company_category": "Clean", "company_logo": false, "company_description": "", }],
    result = allItems.filter(function (a) {
        return Object.keys(a).some(function (k) {
            return a[k] === 'henk';
        });
    });

document.write('<pre>' + JSON.stringify(result, 0, 4) + '</pre>');

Answer 6

If you have a scrambled object, one approach is to loop through all properties and filter out the objects that contain a specific value.

var allItems = [{ "slug": "henk", "company_founded": "2008", "company_category": "Clean", "company_logo": false, "company_description": "", }, { "id": "bas", "company_founded": "2012", "company_category": "Health", "company_logo": false, "company_description": "", }, { "slug": "jan", "company_founded": "2005", "company_category": "Clean", "company_logo": false, "company_description": "", }],
    result = allItems.filter(function (a) {
        return Object.keys(a).some(function (k) {
            return a[k] === 'henk';
        });
    });

document.write('<pre>' + JSON.stringify(result, 0, 4) + '</pre>');

Answer 7

Answer №4

Ensure consistency: Array containing objects (separated by commas, id changed to slug for uniformity.)

The assumption is that the property is unique OR it will fetch the LAST ONE in the sequence. Similar to an ID search or similar process.

MODIFIED to display value within a complex object rather than a simple array EDIT2: include a secondary lookup based on category

var allItems = {"fred":"H fred",rats:"rats",lookupitems: [{
  "slug": "henk",
  "company_founded": "2008",
  "company_category": "Clean",
  "company_logo": false,
  "company_description": "",
} ,{
  "slug": "bas",
  "company_founded": "2012",
  "company_category": "Health",
  "company_logo": false,
  "company_description": "",
}, {
  "slug": "jan",
  "company_founded": "2005",
  "company_category": "Clean",
  "company_logo": false,
  "company_description": "",
}]};

Create a reusable lookup mechanism:

var lookup = {};
var lookupbycategory = {};
// reference the above list and apply it consistently
lookup.list = allItems.lookupitems;
for (var i = 0, len = lookup.list.length; i < len; i++) {
  lookup[lookup.list[i].slug] = lookup.list[i];
  lookupbycategory[lookup.list[i].company_category] = lookup.list[i];
}

Retrieve one item (and use it)

var mychoice = lookup["henk"];
alert(JSON.stringify(mychoice));
alert(JSON.stringify(lookupbycategory["Clean"]));

Reutilize it

var mybas = lookup["bas"];

Answer 8

Ensure consistency: Array containing objects (separated by commas, id changed to slug for uniformity.)

The assumption is that the property is unique OR it will fetch the LAST ONE in the sequence. Similar to an ID search or similar process.

MODIFIED to display value within a complex object rather than a simple array EDIT2: include a secondary lookup based on category

var allItems = {"fred":"H fred",rats:"rats",lookupitems: [{
  "slug": "henk",
  "company_founded": "2008",
  "company_category": "Clean",
  "company_logo": false,
  "company_description": "",
} ,{
  "slug": "bas",
  "company_founded": "2012",
  "company_category": "Health",
  "company_logo": false,
  "company_description": "",
}, {
  "slug": "jan",
  "company_founded": "2005",
  "company_category": "Clean",
  "company_logo": false,
  "company_description": "",
}]};

Create a reusable lookup mechanism:

var lookup = {};
var lookupbycategory = {};
// reference the above list and apply it consistently
lookup.list = allItems.lookupitems;
for (var i = 0, len = lookup.list.length; i < len; i++) {
  lookup[lookup.list[i].slug] = lookup.list[i];
  lookupbycategory[lookup.list[i].company_category] = lookup.list[i];
}

Retrieve one item (and use it)

var mychoice = lookup["henk"];
alert(JSON.stringify(mychoice));
alert(JSON.stringify(lookupbycategory["Clean"]));

Reutilize it

var mybas = lookup["bas"];

Answer 9

Answer №5

One possible approach is to store the data in an object with keys corresponding to specific identifiers. Here's an example:

var itemList = {
  "apple":
    {
        "type": apple,
        "color": "red",
        "taste": "sweet",
        "ripe": true,
        "description": "",
    },
  "banana":
    {
        "type": banana,
        "color": "yellow",
        "taste": "creamy",
        "ripe": true,
        "description": "",
    }
]

This structure allows for quick retrieval of a value like itemList.apple

Using this method results in faster indexing due to logarithmic hash-table lookup instead of linear iteration.

----- edit ----

To optimize lookups, you can preprocess the data by creating a new structure if the cost of generating it is lower than the cost of repeated lookups. For instance:

var itemListByKey = {}
for(var i = 0, l = itemList.length; i<l; i++){
   var item = itemList[i];
   itemListByKey[item.type] = item;
}

Now, itemListByKey will have a similar structure as shown earlier

Answer 10

One possible approach is to store the data in an object with keys corresponding to specific identifiers. Here's an example:

var itemList = {
  "apple":
    {
        "type": apple,
        "color": "red",
        "taste": "sweet",
        "ripe": true,
        "description": "",
    },
  "banana":
    {
        "type": banana,
        "color": "yellow",
        "taste": "creamy",
        "ripe": true,
        "description": "",
    }
]

This structure allows for quick retrieval of a value like itemList.apple

Using this method results in faster indexing due to logarithmic hash-table lookup instead of linear iteration.

----- edit ----

To optimize lookups, you can preprocess the data by creating a new structure if the cost of generating it is lower than the cost of repeated lookups. For instance:

var itemListByKey = {}
for(var i = 0, l = itemList.length; i<l; i++){
   var item = itemList[i];
   itemListByKey[item.type] = item;
}

Now, itemListByKey will have a similar structure as shown earlier

Choosing an element from an array in JavaScript that meets a certain criteria

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

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