I have an array of indexes, called indexSelected. There is also an array of objects called weather. I have put all of the Site Names that that I am dealing with into an array called stationName. I want to sort this array alphabetically whilst keeping the original indexes for that I can refer back to the other properties associated with object. I have tried the method below, however, I cannot seem to get it to work.
var stationName=[];
for (var i=0; i<indexSelected.length; i++) {
stationName.push(weather[indexSelected[i]]["Site Name"]);
}
var copyStationName = stationName.slice(0)
var sortedStationName = stationName.sort();
var originalIndex=[];
for (var i=0; i<stationName.length; i++) {
originalIndex.push(copyStationName.indexOf(sortedStationName[i]))
}
var station=[];
for (var i=0; i<indexSelected.length; i++) {
station.push(weather[originalIndex[i]]["Site Name"]);
}
This station array was to check that the originalIndexes array was correct. It isn't, and I don't know why. I would appreciate some help, or another way to sort this array. I'm looking to put all of the data into a table, sort alphabetically by site name. Thanks
Build an array of objects that carry both the name and index, then use a custom comparison function for the sort. E.g.
var stationInfo = [];
for (var i=0; i<indexSelected.length; i++) {
var idx = indexSelected[i];
stationInfo.push({name: weather[idx]["Site Name"], idx: idx);
}
stationInfo.sort(function(a, b) {
// a & b are the array items (info objects) created above, so make 'em
// point at the `name` property we want to sort by
a = a.name;
b = b.name;
// ... then return -1/0/1 to reflect relative ordering
return a < b ? -1 : (a > b ? 1 : 0);
})
// output a name + index pair
console.log(stationInfo[0].name, stationInfo[0].idx);
Related
I am trying to sort a 2D array of custom objects, inside each inner array, based on one of the properties. This sub-arrays each represent one class, the outer array all the classes in the school. My strategy is as such:
Make a copy of the arry to provide a framework with the correct number of subarrays and indeces
Pass a copy of the sub-array to variable
Iterate over that array (the class) and pull out the last name from the object (which holds a number of other pieces of data on the child) and place it in an array that will be the index
Sort the index
Iterate over the class array, find the position of the last name in the index array, and insert the object into that index into the copied 'school'.
But this is not working. In some instances, one or two objects end up in the wrong place, in other instances it completely out of order. I have tried inspecting my index and comparing it with the 2D array, but the index is correct and I can't figure out why its not working. Here is the code:
var studentsInClass = // I have a function here that returns the 2D array of classes containing custom objects
var sortedStudentsInClass = studentsInClass;
var singleClassHolder = [];
var studentIndex = [];
// each iteration is for a single class
for(var i = 0; i < studentsInClass.length; i ++){
studentIndex = [];
singleClassHolder = studentsInClass[i];
// populate the student reference index
for(var j = 0; j < singleClassHolder.length; j++){
studentIndex.push(singleClassHolder[j].ID);
}
studentIndex.sort();
// iterate through students of single class, placing them in alphabetical order
for(var k = 0; k < singleClassHolder.length; k++){
sortedStudentsInClass[i][studentIndex.indexOf(singleClassHolder[k].ID)] = singleClassHolder[k];
}
}
return sortedStudentsInClass;
}
In case the object is important:
function Child(last, first, id, classroom, serviceDays, eligibility){
this.lastName = last;
this.firstName = first;
this.ID = id;
this.class = classroom;
this.maxServiceDays = serviceDays;
this.eligibility = eligibility;
}
And just a side note, it may seem extraneous having created the new singleClassHolder variable. After I noticed I did that, I removed it and just iterated through the 2D array, but that resulted in even more elements out of place.
Make a copy of the arry
var sortedStudentsInClass = studentsInClass;
This won't make a copy. It only makes one variable reference the other in memory. They both refer to the same array in memory. See related answer here.
The easiest way to fix the code is by declaring sortedStudentsInClass as a new array.
var studentsInClass = get2DArrayOfClasses();
var sortedStudentsInClass = [];
/*...*/
for(var k = 0; k < singleClassHolder.length; k++){
sortedStudentsInClass[i] = sortedStudentsInClass[i] || [];//declare inner array, if not present
sortedStudentsInClass[i][studentIndex.indexOf(singleClassHolder[k].ID)] = singleClassHolder[k];
}
Hello stackoverflow members.
I come with the following problem:
To start we have
var myArray = [[array1],[array2],[array3],[arrayN],...];
where each array is filled with a known number of strings such as
var array1 = ["a","b"], array2 = ["1","2"], array3=["&","é"];....
and so on.
I'm looking for a method to get this result:
expected result ===> a1&;a1é;a2&;a2é;b1&;b1é;b2&;b2é; ....
If the number of dimension were fixed I could use for loops to iterate and build the result, BUT here the problem is that I want to be able to enter N arrays in the main array myArray and by doing so, I change the depth of the nested loops.
If not do you have some ideas to put me on the track of the solution to this?
Thanks!
EDIT by the way this is what i experimented:
for (i=0; i<myArray[0].length; i++){
for (var j =0; j<myArray[1].length; i++){
for(var k = 0; k<myArray[2].length; k++{
console.log(i+j+k);
}
}
}
BTW i can't find a way to describe a function which would nest N for loops where N is myArray.length + 1 (the number of arrays in myArray).
EDIT: i found an iterative way of doing it and wanted to share the solution:JSFiddle
To get a flat list of all cells, something like the following recursive function should work (if you have a non-empty array of arrays, and all array items are strings):
function makeFlatList(inputArray) {
if (inputArray.length == 1) { // if this array has only one array inside
return inputArray[0]; // return the array inside
} else {
var outArr = [];
var arrayShifted = inputArray.slice(1); // remove first subarray from inputarray
var arrayShiftedFlat = makeFlatList(arrayShifted); // recursive call
for (var i=0; i<inputArray[0].length ; i++) { // loop over first array
for (var j=0; j<arrayShiftedFlat.length; j++) {
outArr.push(inputArray[0][i]+arrayShiftedFlat[j]); // add items to outArr
}
}
return outArr;
}
}
Working JSBin here
I have an array of objects, i was trying to iterate over. The array is pretty simple in format.
{a:5, b:"key", c:19}
i was trying to compare an array with a subset, say: [{a:5},...]
for (var i = 0; i < subset.length; i++) {
var searchTerm = subset[i].a;
var index = objs.indexOf(searchTerm, function (el) {
return el.a;
});
if (index > -1) {
objs[index].Found = true;
}
}
So that way ultimately objs, could have a new key in it, 'Found'
This way, it will set the main array objs item.Found = true, if it existed in subset.
There are 2 issues though. Accounting for multiple instances of the same item, and the fact that this current implementation doesnt seem to work.
This is a slight expansion of (indexOf method in an object array? )but with an array of search terms.
ideally, i dont want to change the arrays at all, so im trying not to slice, etc.
In a lot of the defintions, indexOf is defined as:
function indexOf (key, start);
instead of the ideas i am trying to work with.
Edit
Here is some code that i have to get this working, but i was thinking there is a more effecient way to do it than written.
for (var j = 0; j < compare.length; j++){
var searchTerm = compare[j]["a"];
for (var k = 0; k < objs.length; k++){
if (!objs[k].Found && objs[k]["a"] == searchTerm){
objs[k].Found = true;
break;
}
}
}
I have two arrays. The first is for strings and the second is an array for their number of occurrences.
I am trying to get the top 10 most occurrences of words in the first array. I sorted it but somehow I only sort it alphabetically and the second array respectively corresponds to their number of occurrences.
How can I sort the second array from biggest to lowest and, at the same time, sort the first array that match the order of the second?
I'm having trouble inserting my json to my highcharts and I found out why, the numbers should be in square brackets [] I tried already inserting [] in 1 but still does not work please see my post I edit it
this is the data that i should insert in the highchart
[{"name":"#murrayftw","data":[46]},
{"name":"#job","data":[37]},
{"name":"#jobs","data":[25]},
{"name":"#favnashvine","data":[16]},
{"name":"#rollersmusicawards","data":[14]},
{"name":"#soa","data":[13]},
{"name":"#tweetmyjobs","data":[12]},
{"name":"#sman1boyolangu","data":[12]},
{"name":"#supernatural200thepisode","data":[12]},
{"name":"#veteransday","data":[12]}]
Try using a custom compare function with your .sort() call! Check out the documentation here.
I would, in this example (probably not the best way):
Have the unsorted "count" array
Have the unsorted word array
Sort the word array (with a custom function described below)
Sort the count array (no custom function)
The custom compare function would probably be a simple lookup and return the corresponding value in the unsorted count array. (i.e. if the word "a" is 0th index and its relevant count amount is in the 0th index of the count array, return count[0])
If you cannot work with an object try using nested for loops:
var array1 = ['z', 'd', 'e', 'f', 't'], arr1Count = array1.length;
var array2 = [1, 12, 5, 7, 3];
var sortedArray2 = array2.sort(function(x, y) {return y - x});
var i, j, sortedArray1 = [];
for (i = 0; i < arr1Count; i++) {
for (j = 0; j < arr1Count; j++) {
if (array2[j] === sortedArray2[i]) sortedArray1.push(array1[j]); //iterate through the unsorted numeric array (array2) and when it matches the sortedArray2, push this index of array1 into the sortedArray1
}
}
This will create an array of objects that are then sorted by count.
var hashtags = {},
counts = [];
for (var i in data)
{
if(data[i].lang == "en")
{
for (var j in data[i].entities.hashtags)
{
var text = data[i].entities.hashtags[j].text;
if(text) {
if(hashtags[text]) {
hashtags[text].data[0]++;
} else {
hashtags[text] = {
name: text,
data: [1]
};
counts.push(hashtags[text]);
}
}
}
}
}
counts.sort(function(a, b) { return b.data[0] - a.data[0]; });
Simple - don't use 2 arrays but one collection which every element is an object
I took the basics from this post: Sorting JavaScript Object by property value
and completed the demo:
var collection = {car:300, bike:60, motorbike:200, airplane:1000, helicopter:400, rocket:8*60*60}
var sortable = [];
for (var item in collection)
sortable.push([item, collection[item]])
sortable.sort(function(a, b) {return a[1] - b[1]})
collection = {};
for (var i in sortable)
{
collection[sortable[i][0]] = sortable[i][1];
}
console.log(collection);
I have 2 arrays of objects. Each object has an Id property. Now, if I have a 3rd array of just Ids, what is the better and faster way of finding objects from array1 based on those Ids and moving them to array2.
Thanks a lot for answering..
Sample code:
Person = function(id, fn, ln) {
this.id = id,
this.firstName = fn,
this.lastName = ln
}
array1 = new Array();
// add 500 new Person objects to this array
array2 = new Array();
// add some other new Person objects to this array
function moveArrayItems(ids) {
// ids is an array of ids e.g. [1,2,3,4,5,6,...]
// Now I want to find all the person objects from array1 whose ids
// match with the ids array passed into this method. Then move them to array2.
// What is the best way to achive this?
}
If you really have 500+ objects in each array, you're probably better off using a hash to store the objects, keyed by id:
var people = {
1: {id:1, name:"George Washington"},
2: {id:2, name:"John Adams"},
3: {id:3, name:"Thomas Jefferson"}, // ...
}
var people2 = {}
Now it's trivial (and much, much faster) to move things around by ID:
function moveArrayItems(ids) {
var i,id;
for (i=0; i<ids.length; i++){
id = ids[i];
if (people1[id]) {
people2[id] = people1[id];
delete people1[id];
}
}
}
Good question. It actually made me go back and refer the fundamentals. The key thing about a JS array is that its sparse. You can create an array and assign values for any index (eg: 10 and 23). Based on this fact
array1 = new Array();
array1[person1.id] = person1;
array1[person2.id] = person2;
.... goes till N
function moveArrayItems(ids) {
for(index in ids) {
array2.push(array1[ids[index]]);
delete array1[ids[index]];
}
}
NOTE: I am assuming that Person.id is an integer and less than 2^32 - 1. Refer JS documentation if id is greater or a floating point number. The JS Array implementation is not a contiguous block, so don't think assigning a value to index 12345 requires 12345 continuous blocks of memory.
Just some quick untested pseudo code. This gives a O(n^2) algorithm so it may not be best.
function moveArrayItems(ids) {
// ids is an array of ids e.g. [1,2,3,4,5,6,...]
//Now I want to find all the person objects from array1 whose ids match with the ids array passed into this method. Then move them to array2.
//What is the best way to achive this?
for(i = 0;i < ids.length;i++){
var found = false;
var j = 0;
while(!found && j < array1.length){
if(array1[j].id = ids[i]){
array2.push(array1[j]);
found = true;
}
j++;
}
}
}
First a little function by John Resig
// Array Remove - By John Resig (MIT Licensed)
Array.prototype.remove = function(from, to) {
var rest = this.slice((to || from) + 1 || this.length);
this.length = from < 0 ? this.length + from : from;
return this.push.apply(this, rest);
};
Then, merging Vincent's solution
function moveArrayItems(ids)
{
// ids is an array of ids e.g. [1,2,3,4,5,6,...]
// Now I want to find all the person objects from array1
// whose ids match with the ids array passed into
// this method. Then move them to array2.
// What is the best way to achive this?
for(i = 0; i < ids.length; i++)
{
var found = false;
var j = 0;
while(!found && j < array1.length)
{
if(array1[j].id = ids[i])
{
array2.push(array1[j]);
array1.remove(i);
found = true;
}
j++;
}
}
}