I have a parse background job that contains a simple query.each for one class. This class has 2 Arrays field filled with objects.IDs. Inside this query, for every single object, i need to check if the objects.ID of the first Array are contained in the second Array.
Basically in a simple loop:
var j = 0;
for (var j = 0; j < firstArray.length; j++) {
if(firstArray[j] "isContainedIn" secondArray){
// my custom code
}
}
What i can't figure out is the function to use, if exist..Does javascript have a function like that or i need to make a nested loop to achieve my goal?
EDIT: i worked it out using indexOf but the solution proposed by Shqiptar didn't work so here is the one that actually works:
first Array name = usersEligibleToVote
second Array name = usersThatVoted
for (var j = 0; j < usersEligibleToVote.length; j++) {
if(usersThatVoted.indexOf(usersEligibleToVote[j]) === -1){
console.log("user.id "+usersEligibleToVote[j]+" needs to vote");
} else {
console.log("user.id "+usersEligibleToVote[j]+" has voted");
}
}
var j = 0;
for (var j = 0; j < firstArray.length; j++) {
if(firstArray[j].contains(secondArray))
{
// your custom code here
}
}
And then for checking if an object is the same :
var j = 0;
for (var j = 0; j < firstArray.length; j++) {
if(firstArray[j].indexOf(secondArray) != -1)
{
// your custom code here
}
}
I would process it through a simple jQuery and javascript for loop like so:
var arr1;
var arr2;
var i;
for(i = 0; i < arr1.length; i++) {
if ($.inArray(arr1[i], arr2) {
break; //do things here or what not
}
}
Related
Description of problem in code. Why it is going on??
var response = JSON.parse(xhr.responseText);
console.log(response[0].conversationUsers.length); //OK, console outputs "2"
for (i = 0; i < response.length; i++) {
for (j = 0; j < response[i].conversationUsers.length; j++) { //Error 'cannot read property', but it has to be interpreted "j = 0; j < 2; j++" and it worked in console.log
...
}
}
UPD. I've added temporary variable and it works.
for (j = 0; j < response[i].conversationUsers.length; j++) //this way doesn't work
var temp = response[i].conversationUsers;
for (j = 0; j < temp.length; j++) //this way works
Question can be closed, but any ideas why so?
You are using console.log() for only the first object in that array. I suggest you try:
var response = JSON.parse(xhr.responseText);
for (i = 0; i < response.length; i++) {
console.log(response[i].conversationUsers); // should be an array
for (j = 0; j < response[i].conversationUsers.length; j++) {
...
}
}
If you get any undefined in your console, while doing this, you have identified your problem.
The thing is that for the first element in the array response[0].conversationUsers has a value that is an array. That might not be true for every element in that array and therefore some of those elements might not have a length property.
You are trying to iterate inside length property. Try to remove length. Like this
var response = JSON.parse(xhr.responseText);
console.log(response[0].conversationUsers.length);
for (i = 0; i < response; i++) {
for (j = 0; j < response[i].conversationUsers; j++) {
...
}
}
I'm having some issues on how to read arrays.
console.log(arr[i][j]); -- Can someone explain how the i and j fit into this. I'm printing the array i and j to the console, correct?
function multiplyAll(arr) {
var product = 1;
// Only change code below this line
var i = 0;
var j = 0;
for (i = 0; i < arr.length; i++ ) {
for (j = 0; j < arr[i].length; j++) {
console.log(arr[i][j]);
product *= arr[i][j];
}
}
// Only change code above this line
return product;
}
// Modify values below to test your code
multiplyAll([[1,2],[3,4],[5,6,7]]);
You are printing the j-th element of the i-th array to the console.
I have a list of events on a page. My end goal is to hide a purchase button (by adding a class to it) if the event has passed, using JQuery/Javascript. Each event has a 3 data attributes(month, day, year). I tried using the following method to cycle through an array:
var matches = document.querySelectorAll(".event-event");
var i = 0;
for (i = 0; i < matches.length; i++) {
var event = matches[i].getElementsByClassName('date');
var eventDate = event.getAttribute('data-date');
}
But it says that "getAttribute" is not a function, I've also tried ".attr" and it said the same thing.
var matches = document.querySelectorAll(".event-event");
for (var i = 0; i < matches.length; i++) {
var event = matches[i].getElementsByClassName('date');
if (event.length > 0) {
for (var j = 0; j < event.length; j++) {
var eventDate = event[i].getAttribute('data-date');
}
}
}
The getElementsByClassName method returns an array.
Try this:
var matches = document.querySelectorAll(".event-event");
for (var i = 0; i < matches.length; i++) {
var events = matches[i].getElementsByClassName('date');
for(var j = 0; j < events.length; j++) {
var eventDate = events[j].getAttribute('data-date');
}
}
events is an array that you must iterate through.
I've come across writing a piece of code where I wanted to reference the 2D array d2_arr[][] in a loop like so.
for (var i=0; i<d2_arr[i].length; i++) {
//do something
}
Google Script compiler throws an error "cannot read length property from undefined". When I changed [i] for [1], it worked just fine. Could anyone please explain why this is wrong? And a related question: Can a 2D array have a different number of elements in a row? theoretically. An example would be:
[[1,2],[3,4,5],[6,7,8,9],[10,11]]
EDIT. Full code part.
var ids = [];
var j = 0;
for (var i=0; i<d2_arr[i].length; i++){
if (d2_arr[i][2]<=0.05){
ids[j]=d2_arr[i][0];
j++;
}
}
I understood the mistake. Thank you!
You typically need a nested for loop to traverse a 2-D array
var d2_arr = [[1,2],[3,4,5],[6,7,8,9],[10,11]]
for (var i=0; i<d2_arr.length; i++){
for (var j=0; j<d2_arr[i].length; j++){
console.log(d2_arr[i][j] + ' ')
}
}
It is perfectly fine for arrays to be "jagged" and contain uneven sized arrays in the main array.
Here is a fiddle http://jsfiddle.net/7Lr4542s/
Arrays in JS can be of any size and any type. You can combine number and strings in array.
var twoDArray = [[1], ["one", "two"], ["i", "ii", "iii"]];
for(var i = 0; i < twoDArray.length; i++) {
for(var j = 0; j < twoDArray[i].length; j++) {
print(twoDArray[i][j]);
}
}
var threeDArray = [[["1.1.1", "1.1.2"], ["1.2.1", "1.2.2"]], [["1.2.1", "1.2.2"], ["1.2.1", "1.2.2"]], [["2.1.1", "2.1.2"], ["2.2.1", "2.2.2"]], [["2.2.1", "2.2.2"], ["2.2.1", "2.2.2"]]];
for(var i = 0; i < threeDArray.length; i++) {
for(var j = 0; j < threeDArray[i].length; j++) {
for(var k = 0; k < threeDArray[i][j].length; k++) {
print(twoDArray[i][j][k]);
}
}
}
I have a loop to check collision between objects in my game, all the objects are collected in the same Array. I use a code like this to match every object with eachother:
for (var i = 0; i < objs.length; i++) {
for (var j = i + 1; j < objs.length; j++) {
collision(objs[i], objs[j]);
}
}
Now this does not seem to actually perform all collisions with eachother, I've noticed that it skips some too..
Then I came up with this solution:
for (var i = 0; i < objs.length; i++) {
for (var j = 0; j < objs.length; j++) {
if (j != i) {
collision(objs[i], objs[j]);
}
}
}
This solution seem to not have any problems, but I wonder if there is any kinda way to not have to use the if (j != i) statement, or is there maybe a totally different solution?
Soo, who's correct eh..?
It depends on the definition of collision in your game.
If collision is a symmetric function (i.e. A collides with B if, and only if, B collides with A), then use:
for (var i = 0; i < objs.length; i++) {
for (var j = i + 1; j < objs.length; j++) {
collision(objs[i], objs[j]);
}
}
because there's no need to check (B,A) if you checked (A,B) before.
But if it is possible to make A collide with B without making B collide with A, or vice versa, then you must check all possible different pairs, so use
for (var i = 0; i < objs.length; i++) {
for (var j = 0; j < objs.length; j++) {
if (j != i) {
collision(objs[i], objs[j]);
}
}
}