Can you please let me know if it is possible to create dynamically sets of arrays in JS? I tried some thing like this but didn't work
for (i = 0; i < 3; i++) {
var item[i] = [];
}
item1.push(1);
console.log(item1);
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js"></script>
You're almost there. Assuming you're trying to create a two dimensional array (an array of arrays), you just have to declare the top level array and then reference the first level array with [x] array syntax like this:
var items = [];
for (i = 0; i < 3; i++) {
items[i] = [];
}
// Here items is an array of arrays where each first level array entry
// is an empty array. You can then put things into those empty arrays
// You can reference the first level array here
items[1].push(1);
items[1].push(2);
console.log(items[1]); // [1,2]
Related
I have an situation where I have 3 different arrays with very different amounts of objects in it. I've read many questions and blog posts about this but Im still unsure when to use what.
PS! My biggest problem is that I need to iterate and push (perfect for arrays), also find if exists in array and delete (more suitable for objects). Specific order is not required.
I can't allow having same object in both array1 and array1clicked
because they should perform different actions.
When it's best to use object and when array in my example? What should I replace with object and what should stay as array? Im pretty sure that amounts of objects in it also matters, right?
My current code:
//Objects in arrays are literally custom {objects} with custom prototypes and html
var array1 = [ 20 objects ];
var array1clicked = [];
var array2 = [ 250 objects ];
var array2clicked = [];
var array3 = [ 50 000 objects ];
var array3clicked = [];
//Each object in arrays has event attached
objecthtml.click(function() {
//Add to clicked array
array1clicked.push(thisobject);
//Remove from initial array
var index = array1.indexOf(thisobject);
if (index > -1) {
array1.splice(index, 1);
}
}
//Same with array2 and array3 objects
//Iterations on different conditions
var array1count = array1.length;
var array1clickedcount = array1clicked.length;
//Same with array2 and array3
if(condition1) {
for(a = 0; a < array1count; a++) {
array1[a].div.style.visibility = 'hidden';
}
//Same with array2 and array3 objects
for(a = 0; a < array1clickedcount; a++) {
array1clicked[a].div.style.visibility = 'visible';
}
//Same with array2clicked and array3clicked objects
}
else if(condition2) {
for(a = 0; a < array1count; a++) {
array1[a].div.style.visibility = 'visible';
}
//Same with array2 and array3 objects
for(a = 0; a < array1clickedcount; a++) {
array1clicked[a].div.style.visibility = 'hidden';
}
//Same with array2clicked and array3clicked objects
}
It seems you want a data structure with these operations:
Iteration
Insert
Delete
Search
With arrays, the problem is that searches and deletions (with reindexing) are slow.
With objects, the problem is that the property names can only be strings.
The perfect structure is a set.
var s = new Set();
s.add(123); // insert
s.has(123); // search
s.delete(123); // delete
s.values(); // iterator
In your case, I think you have to use just Array.
In common case, you could use object to keep references and push some values into it, but If you wanna iterate on this, I think you have to use Array.
This is my code
$scope.students=[];
$scope.students[[object Object][object Object]]
[0]{"id":"101","name":"one","marks":"67"}
[1]{"id":"102","name":"two","marks":"89"}
i want to convert into following format like.
$scope.students=[{"id":"101","name":"one","marks":"67"},{"id":"102","name":"two","marks":"89"}]
i tried using .map function but not working,now i want to convert array of arrays into array of objects format by using angularjs.
If students variable is a two dimensional array such as below:
students = [[{"id":"101","name":"one","marks":"67"}, {"id":"102","name":"two","marks":"89"}]]
You can do double loop to loop through each array of objects, then push each object into an array you want to save it into. Below is vanilla JavaScript, but I am sure there are different ways to do it.
var students = [];
var results = [];
students = [[{"id":"101","name":"one","marks":"67"}, {"id":"102","name":"two","marks":"89"}]]
console.log(students); //array of array
console.log('-----');
console.log(students[0]); //array of object
console.log('-----');
for (i = 0; i < students.length; i++) {
console.log(students[i]); //the array of object
for(var j=0; j < students[i].length; j++){
results.push(students[i][j]);
}
}
console.log('--Results---');
console.log(results);
Also check my JSBin: https://jsbin.com/tareku/edit?html,js,console
I have an array like below in java-script
Result = [
{"ID":1,"Type":"Pyramid","Phase":"One"},
{"ID":2,"Type":"Pyramid","Phase":"Two"}
]
I tried accessing the individual values and was able to by the below code
alert(Result[0].ID) or alert(Result[0].Phase)
Is there a way to access this by index? like Result[0][1], i tried but getting [object][object]
also i need to access column count
Please help me
You have array of object and by using for loop you can easily access all element value.
try following
function getValue() {
var keys ;
var Result = [{"ID":1,"Type":"Pyramid","Phase":"One"}, {"ID":2,"Type":"Pyramid","Phase":"Two"}]
for(var i=0; i<Result.length;i++){
keys = [];
for(var k in Result[i]){
keys.push(k);
}
for(var k=0;k<keys.length;k++){
console.log(keys[k]+"="+ Result[i][keys[k]]);
}
console.log("key count =" +keys.length);
}
}
CHECK THIS
from https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys
alert(Result[0][Object.keys(Result[0])[0]]);
Result[0] gets the first row
Object.keys(Result[0]) gets the keys in the first row
Object.keys(Result[0])[0] gets the first column name.
Object.keys(Result[0]).length is the column count in the first row.
Also, objects are not indexed based on a linear integer index as arrays are, so assigning ordered numbers to the unordered list of keys is not right.
A two dimensional array would look like this:
Result = [
[1,"Pyramid","One"],
{2,"Pyramid","Two"}
]
in this case, you could address each field like so: Result[row][col] thus Result[0][2] would yield One.
To access fields in an array of object use the syntax you have provided. Also, why would you want to access the fields in your objects based on id? Or why would you not use an array of arrays?
Your Result is an array of object, then you must first get an object, and then get the property of your object. This is not a multidimensional array.
You array has an object we have to convert that object to array. So converting whole var Result to newResult you can access newResult and it's component through index number
Result = [
{"ID":1,"Type":"Pyramid","Phase":"One"},
{"ID":2,"Type":"Pyramid","Phase":"Two"}
];
var newResult = [];
for (var i = 0; i < Result.length; i++) {
newResult[i] = [];
for (var x in Result[i]) {
if (Result[i].hasOwnProperty(x)) {
newResult[i].push(Result[i][x]);
}
};
};
console.log(newResult);
Use newResult instead of Result
You can get ID by newResult[0][0]
http://jsfiddle.net/LLz1cbok/
Suppose I have a global object that looks like this:
var TheFruits = {
323: {},
463: {},
223: {} ..... // can be thousands of properties
}
Basically, the keys are IDs and the values are themselves objects. Now suppose I have an array of IDs that I pass into a function and I want that function to return an array of references to the values that match the IDs of the global object (ie. no deep copy). Something like this:
function GetReferences(TheArrayOfIDs) {
var TheArrayOfReferences = [];
return TheArrayOfReferences;
}
Now I know I can write a for loop that iterates over TheArrayOfIDs and that then loops over the object keys at each iteration but then that's a loop within a loop. So I'm looking for the fastest way of doing it, and jquery is available.
Basically, if TheArrayOfIDs = [323, 463, 223]; then TheArrayOfReferences =[TheFruit.323, TheFruit.463, TheFruit.223];
Thanks.
You don't need a second loop:
var results = [];
for (var i = 0; i < ids.length; i++)
results.push(fruits[ids[i]]);
You have to do only one loop as key look-up is built-in :
var TheArrayOfReferences = TheArrayOfIDs.map(function(id){return TheFruits[id]});
Something like that should work :
var i = 0, l = TheArrayOfIDs.length;
for (i = 0; i < l; i++)
TheArrayOfReferences.push(TheFruits[TheArrayOfIDs[i]]);
Consider this Array
var LIST =[];
LIST['C']=[];
LIST['B']=[];
LIST['C']['cc']=[];
LIST['B']['bb']=[];
LIST['C']['cc'].push('cc0');
LIST['C']['cc'].push('cc1');
LIST['C']['cc'].push('cc2');
LIST['B']['bb'].push('bb0');
LIST['B']['bb'].push('bb1');
LIST['B']['bb'].push('bb2');
I can loop through this array like
for(var i in LIST){
console.log(i)//C,B
var level1=LIST[i];
for(var j in level1){
console.log(j)//cc,bb
// etc...
}
}
Fine.. I have few basic questions.
1.How to sort the array in each level?
One level can be sort by .sort(fn) method . How can i pass to inner levels?
2.Why the indexOf method does not works to find the elements in first two levels?
If it's because of the a non string parameter .. how can i search an array items in array if the item is not string?
3.How for(var i in LIST) works ?
I just need a basic understanding of indexing and looping through array ..
Thanks ..
LIST is NOT a three dimensional array in Javascript, it is just an array.
//declare an array which names LIST.
var LIST = [];
//set a property named 'C' of the LIST to be an array.
LIST['C']=[];
//set a property named 'B' of the LIST to be an array.
LIST['B']=[];
//set a property named 'cc' of the 'LIST.C'(which is an array object)
LIST['C']['cc']=[];
//set a property named 'bb' of the 'LIST.B'(which is an array object)
LIST['B']['bb']=[];
The fact is you only need to let the last level to be an array, see my example code below.
function iterateOrderd(obj) {
if (obj instanceof Array) {
obj.sort();
for (var j = 0, l=obj.length; j < l; j++) {
console.log(obj[j]);
}
} else {
var sortable = [];
for (var i in obj) {
if (obj.hasOwnProperty(i)) {
sortable.push(i);
}
}
sortable.sort();
for (var j = 0, l=sortable.length; j < l; j++) {
console.log(sortable[j]);
iterateOrderd(obj[sortable[j]]);
}
}
}
var LIST = {};
LIST['C'] = {};
LIST['B'] = {};
LIST['C']['cc']=[];
LIST['B']['bb']=[];
LIST['C']['cc'].push('cc0');
LIST['C']['cc'].push('cc1');
LIST['C']['cc'].push('cc2');
LIST['B']['bb'].push('bb0');
LIST['B']['bb'].push('bb1');
LIST['B']['bb'].push('bb2');
iterateOrderd(LIST);
You need to know that Array inherits from Object.
In JavaScript, any Object instance is an associative array(!), so acts like an Array in PHP. For example:
var o = {}; // or new Object();
o['foo'] = 'bar';
o[0] = 'baz';
for (i in o) { console.log(i, o[i]); }
Sorting an Object does not make much sense. indexOf would kinda work in theory, but is not implemented.
Arrays are ordered lists. Array instances have push(), length, indexOf(), sort() etc., but those only work for numerical indexes. But again, Array inherits from Object, so any array can also contain non-numerical index entries:
var a = []; // or new Array();
a[0] = 'foo'; // a.length is now 1
a.push('baz'); // a[1] === 'baz'
a.qux = 1; // will not affect a.length
a.sort(); // will not affect a.qux
for (i in a) { console.log(i, a[i]); }
I recommend playing around with arrays and objects, and you'll soon get the point.
What is your sorting criteria ? I mean how will you say array firstArray comes before secondArray?
regarding the for (counter in myArray), counter will take values of an array element in every iteration.
for (counter in [0,1,5]), counter will have values 0, 1 and 5 in the 3 iterations.
In your case, i will have values LIST['B'] and LIST['C'] in the two iterations and j will have values LIST['B']['bb'], LIST['B']['cc'], LIST['C']['bb'] and LIST['C']['cc'].
Both i and j will be arrays.