I have a variable which is an array and I want every element of the array to act as an object by default. To achieve this, I can do something like this in my code.
var sample = new Array();
sample[0] = new Object();
sample[1] = new Object();
This works fine, but I don't want to mention any index number. I want all elements of my array to be an object. How do I declare or initialize it?
var sample = new Array();
sample[] = new Object();
I tried the above code but it doesn't work. How do I initialize an array of objects without using an index number?
Use array.push() to add an item to the end of the array.
var sample = new Array();
sample.push(new Object());
To do this n times use a for loop.
var n = 100;
var sample = new Array();
for (var i = 0; i < n; i++)
sample.push(new Object());
Note that you can also substitute new Array() with [] and new Object() with {} so it becomes:
var n = 100;
var sample = [];
for (var i = 0; i < n; i++)
sample.push({});
Depending on what you mean by declaring, you can try using object literals in an array literal:
var sample = [{}, {}, {} /*, ... */];
EDIT: If your goal is an array whose undefined items are empty object literals by default, you can write a small utility function:
function getDefaultObjectAt(array, index)
{
return array[index] = array[index] || {};
}
Then use it like this:
var sample = [];
var obj = getDefaultObjectAt(sample, 0); // {} returned and stored at index 0.
Or even:
getDefaultObjectAt(sample, 1).prop = "val"; // { prop: "val" } stored at index 1.
Of course, direct assignment to the return value of getDefaultObjectAt() will not work, so you cannot write:
getDefaultObjectAt(sample, 2) = { prop: "val" };
You can use fill().
let arr = new Array(5).fill('lol');
let arr2 = new Array(5).fill({ test: 'a' });
// or if you want different objects
let arr3 = new Array(5).fill().map((_, i) => ({ id: i }));
Will create an array of 5 items. Then you can use forEach for example.
arr.forEach(str => console.log(str));
Note that when doing new Array(5) it's just an object with length 5 and the array is empty. When you use fill() you fill each individual spot with whatever you want.
After seeing how you responded in the comments. It seems like it would be best to use push as others have suggested. This way you don't need to know the indices, but you can still add to the array.
var arr = [];
function funcInJsFile() {
// Do Stuff
var obj = {x: 54, y: 10};
arr.push(obj);
}
In this case, every time you use that function, it will push a new object into the array.
You don't really need to create blank Objects ever. You can't do anything with them. Just add your working objects to the sample as needed. Use push as Daniel Imms suggested, and use literals as Frédéric Hamidi suggested. You seem to want to program Javascript like C.
var samples = []; /* If you have no data to put in yet. */
/* Later, probably in a callback method with computed data */
/* replacing the constants. */
samples.push(new Sample(1, 2, 3)); /* Assuming Sample is an object. */
/* or */
samples.push({id: 23, chemical: "NO2", ppm: 1.4}); /* Object literal. */
I believe using new Array(10) creates an array with 10 undefined elements.
You can instantiate an array of "object type" in one line like this (just replace new Object() with your object):
var elements = 1000;
var MyArray = Array.apply(null, Array(elements)).map(function () { return new Object(); });
Well array.length should do the trick or not? something like, i mean you don't need to know the index range if you just read it..
var arrayContainingObjects = [];
for (var i = 0; i < arrayContainingYourItems.length; i++){
arrayContainingObjects.push {(property: arrayContainingYourItems[i])};
}
Maybe i didn't understand your Question correctly, but you should be able to get the length of your Array this way and transforming them into objects. Daniel kind of gave the same answer to be honest. You could just save your array-length in to his variable and it would be done.
IF and this should not happen in my opinion you can't get your Array-length. As you said w/o getting the index number you could do it like this:
var arrayContainingObjects = [];
for (;;){
try{
arrayContainingObjects.push {(property: arrayContainingYourItems[i])};
}
}
catch(err){
break;
}
It is the not-nice version of the one above but the loop would execute until you "run" out of the index range.
//making array of book object
var books = [];
var new_book = {id: "book1", name: "twilight", category: "Movies", price: 10};
books.push(new_book);
new_book = {id: "book2", name: "The_call", category: "Movies", price: 17};
books.push(new_book);
console.log(books[0].id);
console.log(books[0].name);
console.log(books[0].category);
console.log(books[0].price);
// also we have array of albums
var albums = []
var new_album = {id: "album1", name: "Ahla w Ahla", category: "Music", price: 15};
albums.push(new_album);
new_album = {id: "album2", name: "El-leila", category: "Music", price: 29};
albums.push(new_album);
//Now, content [0] contains all books & content[1] contains all albums
var content = [];
content.push(books);
content.push(albums);
var my_books = content[0];
var my_albums = content[1];
console.log(my_books[0].name);
console.log(my_books[1].name);
console.log(my_albums[0].name);
console.log(my_albums[1].name);
This Example Works with me.
Snapshot for the Output on Browser Console
Try this-
var arr = [];
arr.push({});
const sample = [];
list.forEach(element => {
const item = {} as { name: string, description: string };
item.name= element.name;
item.description= element.description;
sample.push(item);
});
return sample;
Anyone try this.. and suggest something.
Use array.push() to add an item to the end of the array.
var sample = new Array();
sample.push(new Object());
you can use it
var x = 100;
var sample = [];
for(let i=0; i<x ;i++){
sample.push({})
OR
sample.push(new Object())
}
Using forEach we can store data in case we have already data we want to do some business login on data.
var sample = new Array();
var x = 10;
var sample = [1,2,3,4,5,6,7,8,9];
var data = [];
sample.forEach(function(item){
data.push(item);
})
document.write(data);
Example by using simple for loop
var data = [];
for(var i = 0 ; i < 10 ; i++){
data.push(i);
}
document.write(data);
If you want all elements inside an array to be objects, you can use of JavaScript Proxy to apply a validation on objects before you insert them in an array. It's quite simple,
const arr = new Proxy(new Array(), {
set(target, key, value) {
if ((value !== null && typeof value === 'object') || key === 'length') {
return Reflect.set(...arguments);
} else {
throw new Error('Only objects are allowed');
}
}
});
Now if you try to do something like this:
arr[0] = 'Hello World'; // Error
It will throw an error. However if you insert an object, it will be allowed:
arr[0] = {}; // Allowed
For more details on Proxies please refer to this link:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy
If you are looking for a polyfill implementation you can checkout this link:
https://github.com/GoogleChrome/proxy-polyfill
The below code from my project maybe it good for you
reCalculateDetailSummary(updateMode: boolean) {
var summaryList: any = [];
var list: any;
if (updateMode) { list = this.state.pageParams.data.chargeDefinitionList }
else {
list = this.state.chargeDefinitionList;
}
list.forEach((item: any) => {
if (summaryList == null || summaryList.length == 0) {
var obj = {
chargeClassification: item.classfication,
totalChargeAmount: item.chargeAmount
};
summaryList.push(obj);
} else {
if (summaryList.find((x: any) => x.chargeClassification == item.classfication)) {
summaryList.find((x: any) => x.chargeClassification == item.classfication)
.totalChargeAmount += item.chargeAmount;
}
}
});
if (summaryList != null && summaryList.length != 0) {
summaryList.push({
chargeClassification: 'Total',
totalChargeAmount: summaryList.reduce((a: any, b: any) => a + b).totalChargeAmount
})
}
this.setState({ detailSummaryList: summaryList });
}
var ArrayofObjects = [{}]; //An empty array of objects.
Related
I have 2 arrays namely,
configdata = ["assignee", "shortDesc"];
ticketarray = ["Tom","testDesc"];
I want to store the values as a key value pair in another array, something like this:
ticketData = ["assignee":"Tom","shortDesc":"testDesc"];
Kindly note that the array values are dynamic, so I cannot hardcode them.
Is there a way to do so? I am able to achieve the above said requirement but the length always shows 0. This is the code that I am using:
configdata.Incident_Field.forEach(function (k, i) {
this[k] = ticketarray[i];
}, ticketData);
Other people have explained why your code did not work. I am providing another solution using reduce.
const configdata = ["assignee", "shortDesc"];
const ticketarray = ["Tom", "testDesc"];
let ticketData = configdata.reduce((result, value, index) => {
result[value] = ticketarray[index];
return result;
}, {});
console.log(ticketData);
Output:
{
assignee: "Tom",
shortDesc: "testDesc"
}
The below is not a valid structure in JavaScript:
ticketData = ["assignee":"Tom","shortDesc":"testDesc"];
What you need is a JavaScript object. The best you can do is:
Make sure both the array lengths are same.
Associate the key and value by creating a new object.
Use Object.keys(obj).length to determine the length.
Start with the following code:
configdata = ["assignee", "shortDesc"];
ticketarray = ["Tom", "testDesc"];
if (configdata.length == ticketarray.length) {
var obj = {};
for (var i = 0; i < configdata.length; i++)
obj[configdata[i]] = ticketarray[i];
}
console.log("Final Object");
console.log(obj);
console.log("Object's Length: " + Object.keys(obj).length);
The above will give you an object of what you liked, a single variable with all the values:
{
"assignee": "Tom",
"shortDesc": "testDesc"
}
I know it's simple, but I don't get it.
I have this code:
// My object
const nieto = {
label: "Title",
value: "Ramones"
}
let nietos = [];
nietos.push(nieto.label);
nietos.push(nieto.value);
If I do this I'll get a simple array:
["Title", "Ramones"]
I need to create the following:
[{"01":"Title", "02": "Ramones"}]
How can I use push() to add the object into the nietos array?
You have to create an object. Assign the values to the object. Then push it into the array:
var nietos = [];
var obj = {};
obj["01"] = nieto.label;
obj["02"] = nieto.value;
nietos.push(obj);
Create an array of object like this:
var nietos = [];
nietos.push({"01": nieto.label, "02": nieto.value});
return nietos;
First you create the object inside of the push method and then return the newly created array.
can be done like this too.
// our object array
let data_array = [];
// our object
let my_object = {};
// load data into object
my_object.name = "stack";
my_object.age = 20;
my_object.hair_color = "red";
my_object.eye_color = "green";
// push the object to Array
data_array.push(my_object);
Using destructuring assignment (ES6)
const nieto = {label: 'title', value: 'ramones' }
const modifiedObj = {01: nieto.label, 02: nieto.value}
let array = [
{03: 'asd', 04: 'asd'},
{05: 'asd', 06: 'asd'}
]
// push the modified object to the first index of the array
array = [modifiedObj, ...array]
console.log(array)
If you'd like to push the modified object to the last index of the array just change the destructured array ...array to the front.
array = [...array, modifiedObj]
Well, ["Title", "Ramones"] is an array of strings. But [{"01":"Title", "02", "Ramones"}] is an array of object.
If you are willing to push properties or value into one object, you need to access that object and then push data into that.
Example:
nietos[indexNumber].yourProperty=yourValue; in real application:
nietos[0].02 = "Ramones";
If your array of object is already empty, make sure it has at least one object, or that object in which you are going to push data to.
Let's say, our array is myArray[], so this is now empty array, the JS engine does not know what type of data does it have, not string, not object, not number nothing. So, we are going to push an object (maybe empty object) into that array. myArray.push({}), or myArray.push({""}).
This will push an empty object into myArray which will have an index number 0, so your exact object is now myArray[0]
Then push property and value into that like this:
myArray[0].property = value;
//in your case:
myArray[0]["01"] = "value";
I'm not really sure, but you can try some like this:
var pack = function( arr ) {
var length = arr.length,
result = {},
i;
for ( i = 0; i < length; i++ ) {
result[ ( i < 10 ? '0' : '' ) + ( i + 1 ) ] = arr[ i ];
}
return result;
};
pack( [ 'one', 'two', 'three' ] ); //{01: "one", 02: "two", 03: "three"}
The below solution is more straight-forward. All you have to do is define one simple function that can "CREATE" the object from the two given items. Then simply apply this function to TWO arrays having elements for which you want to create object and save in resultArray.
var arr1 = ['01','02','03'];
var arr2 = ['item-1','item-2','item-3'];
resultArray = [];
for (var j=0; j<arr1.length; j++) {
resultArray[j] = new makeArray(arr1[j], arr2[j]);
}
function makeArray(first,second) {
this.first = first;
this.second = second;
}
This solution can be used when you have more than 2 properties in any object.
const nieto = {
label: "Title",
value: "Ramones"
}
let nietos = [];
let xyz = Object.entries(nieto)
xyz.forEach((i,j)=>{
i[0] = `${(j+1).toLocaleString("en-US", {
minimumIntegerDigits: 2,
useGrouping: false,
})}`
})
nietos.push(Object.fromEntries(xyz))
Very similar to this question:
Javascript: how to dynamically create nested objects using object names given by an array
Instead of calling
assign(obj, keyPath, value)
example of usage of the previously answer:
var accountinfo = {}
assign(accountinfo, ["name", "addressinfo", "zipcode"], "90210");
That will output:
accountinfo = {name: "", addressinfo: {zipcode:"90210"}};
Now, I'd like to support arrays... in the above example, I'd like to support multiple addressinfo per account. I'd like to say:
assign(accountinfo, ["name", "addressinfo[1]", "zipcode"], "90210");
The result would be:
accountinfo = {name: "", addressinfo: [{},{zipcode:"90210"}]}
var regex = /\[([0-9]+)\]/ will show me the # inside the brackets, but I'm not sure how I'd have to iterate through each element in the array to make sure it exists (and create it if it doesn't).. and the difficult part, support this for each array element submitted as part of the function (I'd like to say :
assign(accountinfo, ["family", "name[3]", "addressinfo[1]", "zipcode"], "90210");
Edit:
Figured it out.
function assign(obj, keyPath, value) {
keyPath = keyPath.split(‘.’);
lastKeyIndex = keyPath.length - 1;
var re = /^(.+?)\[*(\d+)*\]*$/;
for (var i = 0; i < lastKeyIndex; i++) {
key = keyPath[i];
var ind;
var middle = re.exec(key);
key = middle[1];
ind = middle[2];
if (ind) {
if (!(obj[key]))
obj[key] = [];
if (!(obj[key][ind]))
obj[key][ind] = {};
}
if (!(key in obj))
obj[key] = {};
if (ind)
obj = obj[key][ind];
else
obj = obj[key];
}
obj[keyPath[lastKeyIndex]] = value;
}
The simplest question ever, and I did not find right answer yet.
Got object list: object_list = {}
Got object: object_x = {...}
How do I add object_x to object_list[objects_x]?
I tried: object_list[objects_x][object_list[objects_x].length] = object_x, but object_list[objects_x].length is undefined.
push() does not work either.
Do I really need to define external counter for that?
PLEASE NOT THAT I MEAN LIST OF LISTS OF OBJECTS. NOTE THE DIFFERENCE BETWEEN objects_x and object_x.
There is no simple solution like in PHP where you simply $array['something'][] = $somedata ?
object_list['object_x'] = object_x;
// or
object_list.object_x = object_x;
console.log(object_list.object_x === object_list['object_x'])
How to work with objects - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Working_with_Objects
When you create a variable like var stuff = {}, you're creating an empty object literal, it has no attributes (properties or methods) other than what it inherits from Object. If you want to keep objects stored in various lists in this object you need to first create those lists.
var stuff = { shelves: [], selectors: [], images: [], additional: [] };
Now you can add whatever you want to those lists as much as you want.
var image = { src: '/path/to/image.jpg' };
stuff.images.push(image);
You can add more lists to stuff whenever like by just setting the new property on stuff.
stuff.some_other_list = []
Hope it helps.
Your base assumption is wrong.
This:
var object_list = {}
Is not a list. It's not an array and you can't reference its items by index, thus it also does not have .length property.
What you are after is a plain array:
var object_list = [];
Now you can push items into it:
object_list.push(object_x);
Edit: based on your comments and edits, I think what you're really after are couple of helper functions:
function AddToList(list, item) {
var counter = 0;
for (var key in list)
counter++;
var key = "item_index_" + counter;
list[key] = item;
}
function GetItemByIndex(list, index) {
var counter = 0;
var existingKey = "";
for (var key in list) {
if (counter == index) {
existingKey = key;
break;
}
counter++;
}
return (existingKey.toString().length > 0) ? list[existingKey] : null;
}
Having those, you can have such a code now:
var mainList = {};
var newItem = { "foo": "bar" };
AddToList(mainList, newItem);
var dummy = GetItemByIndex(mainList, 0)["foo"]; //will contain "bar"
Live test case.
If you are interested use object, not array, you can use like this:
var object_list = {};
var object_x = {'prop1':'val1'};
// add object
object_list.myobj = object_x;
// for access, same scheme.
object_list.myobj.prop1 = 'valX';
// for loop thru
for (var key in object_list) {
var obj = object_list[key];
obj.prop1 = 'valY';
}
I have an array into which I insert a load of values along with their corresponding keys. They are inserted fine as I can see them all in the array when I do a console.log.
The issue is, I can't seem to retrieve the values from the array using their respective keys.
Here is my code.
var personArray = [];
personArray.push({
key: person.id,
value:person
});
var personID = person.id;
console.log(personArray.personID);
I have also tried console.log(personArray[personID]; but this does not work either.
The value I get in my console is undefined.
What you are doing is that you push dictionaries into the array. If person.id is unique, then you can do this:
var personDict = {}
personDict[person.id] = person
and then personDict[personID] will work. If you want to keep your structure, then you have to search inside the array for it:
var personArray = [];
personArray.push({
key: person.id,
value:person
});
var personID = person.id;
var search = function(id) {
var l = personArray.length;
for (var i = 0; i < l; i++) {
var p = personArray[i];
if (p.key === id) {
return p.value;
}
}
return null;
};
search(personID);
You can use dictionary format as suggested by #freakish,
Or use the filter function to find the required object.
For example:
var personArray = [];
var person = {id: 'aki', value:'Akhil'}
personArray.push({
key: person.id,
value:person
});
personArray.filter(function(item){
return item.key == 'aki'
});