Acces a multidimensional array from database and save it - javascript

I have a 2D array that I get from a database. It looks like that:
arrayDB = [url1,name1,url2,name2,url3,name3, ...]
Now I want to save this array within my code. I tried:
function symbolsArray(syms){
var tableArray = [];
var tableArray2 = [];
for (var i = 0; i < syms.length; i++) {
tableArray[i] = syms[i][0]; //url
tableArray2[i] = syms[i][1]; //Name
}
}
However, this approach is not really suitable because I would need two return values. Is there maybe a better approach or a way to solve the content in a 2D array?
Syms is the data from the database.

Do take a look at
How can I create a two dimensional array in JavaScript?
that answers similar question about 2d arrays in javascript. Try something like-
function symbolsArray(syms){
var tableArray = [];
for (var i = 0; i < syms.length; i++) {
tableArray[i] = [syms[i][0] , syms[i][1]];
}
}

Your array is not two dimensional.You can seperate urls and names like this...
arrayDB = ['url1','name1','url2','name2','url3','name3'];//assumed array
urls = [];//array for urls
names = [];//array for names
for(i=0;i<arrayDB.length;i++){
(i%2==0)?urls.push(arrayDB[i]):names.push(arrayDB[i]);
}
console.log(names);
console.log(urls);

If ive got you right, your problem is that your code needs to return two things, but return does just one, right?
May Return an Object:
return {names: tableArray2,urls:tableArray};
You could use it like this:
var mydata=symbolsArray(arrayDB);
console.log(mydata.names,mydata.urls);
If you just want to deep clone, do:
var cloned=JSON.parse(JSON.stringify(arrayDB));
Or more elegantly:
var cloned=arrayDB.map(el=>el.map(e=>e));

Related

How can I create an array from an input string using JavaScript?

Currently I have a PHP page returning some values. The data is something like this:
08-30-2018, in
08-29-2018, out
08-28-2018, in
08-27-2018, in
How can I create a custom array in Javascript with the values above to be similar as this array below:
var system = [
['08-30-2018', 'in'],
['08-29-2018', 'out'],
['08-28-2018', 'in'],
['08-27-2018', 'in']
];
I have tried array.push, but it does not create an array like above.
What should I do? Can you help me? Thank you!
You can use multi-dimensional arrays in JavaScript
var system = [];
var output = "08-30-2018, in\n08-29-2018, out\n08-28-2018, in\n08-27-2018, in";
var items = output.split("\n");
for(i=0; i<items.length; i++){
var data = items[i].split(",");
var item = [];
item.push(data[0].trim());
item.push(data[1].trim());
system.push(item);
}
console.log(system);
You could also parse this kind of input using regular expressions:
const input = '08-30-2018, in\n08-29-2018, out\n08-28-2018, in\n08-27-2018, in';
const regex = /(\d{2}-\d{2}-\d{4}), (in|out)/g;
let system = [];
let match;
while ((match = regex.exec(input)) !== null) {
system.push([match[1], match[2]]);
}

Sorting 2D javascript array

I have an array containing a list of tags and count.
tags_array[0] = tags;
tags_array[1] = tags_count;
I need to sort the arrays base on the count so that I can pick out the top few tags.
Sort one, while storing the sort comparisons. Then sort the other using those results:
var res = [];
tags_count.sort( function( a, b ){ return res.push( a=a-b ), a; } );
tags.sort( function(){ return res.shift(); } );
Supposing tags and tags_count are 2 arrays of same length, I would first build a proper array of objects :
var array = [];
for (var i=0; i<tags_count.length; i++) {
array.push({tag:tags[i], count:tags_count[i]});
}
And then sort on the count :
array.sort(function(a, b) {return a.count-b.count});
If you need to get your arrays back after that, you may do
for (var i=0; i<array.length; i++) {
tags[i] = array[i].tag;
tags_count[i] = array[i].count;
}
Demonstration
Assuming that both tags and tags_count are arrays with the same length (that part of the question wasn't too clear), the following is one way to do the trick.
var tags_array = new Array();
for (var i = 0; i < tags.length; i++)
{
tags_array[i] = {};
tags_array[i].tagName = tags[i];
tags_array[i].tagCount = tags_count[i];
}
tags_array.sort(function(a,b){return b.tagCount-a.tagCount});
One should note that it might be possible to structure the data in this way from the start instead of rewriting it like this, in which case that is preferable. Likewise, a better structure can be used to save the data, but this will work.

How to "clean" an array in javascript?

I am stuck here. How can I clean this array:
{"data":[{"id":"5201521d42"},{"id":"52049e2591"},{"id":"52951699w4"}]}
So that it looks like:
["5201521d42","52049e2591","52951699w4"]
I am using Javascript.
You just need to iterate over the existing data array and pull out each id value and put it into a new "clean" array like this:
var raw = {"data":[{"":"5201521d42"},{"id":"52049e2591"},{"id":"52951699w4"}]};
var clean = [];
for (var i = 0, len = raw.data.length; i < len; i++) {
clean.push(raw.data[i].id);
}
Overwriting the same object
var o = {"data":[{"id":"5201521d42"},{"id":"52049e2591"},{"id":"52951699w4"}]};
for (var i = o.data.length; i--; ){
o.data[i] = o.data[i].id;
}
What you're doing is replacing the existing object with the value of its id property.
If you can use ES5 and performance is not critical, i would recommend this:
Edit:
Looking at this jsperf testcase, map vs manual for is about 7-10 times slower, which actually isn't that much considering that this is already in the area of millions of operations per second. So under the paradigma of avoiding prematurely optimizations, this is a lot cleaner and the way forward.
var dump = {"data":[{"id":"5201521d42"},{"id":"52049e2591"},{"id":"52951699w4"}]};
var ids = dump.data.map(function (v) { return v.id; });
Otherwise:
var data = dump.data;
var ids = [];
for (var i = 0; i < data.length; i++) {
ids.push(data[i].id);
}
Do something like:
var cleanedArray = [];
for(var i=0; i<data.length; i++) {
cleanedArray.push(data[i].id);
}
data = cleanedArray;
Take a look at this fiddle. I think this is what you're looking for
oldObj={"data":[{"":"5201521d42"},{"id":"52049e2591"},{"id":"52951699w4"}]};
oldObj = oldObj.data;
myArray = [];
for (var key in oldObj) {
var obj = oldObj[key];
for (var prop in obj) {
myArray.push(obj[prop]);
}
}
console.log(myArray)
Use Array.prototype.map there is fallback code defined in this documentation page that will define the function if your user's browser is missing it.
var data = {"data":[{"":"5201521d42"},{"id":"52049e2591"},{"id":"52951699w4"}]};
var clean_array = [];
for( var i in data.data )
{
for( var j in data.data[i] )
{
clean_array.push( data.data[i][j] )
}
}
console.log( clean_array );
You are actually reducing dimension. or you may say you are extracting a single dimension from the qube. you may even say selecting a column from an array of objects. But the term clean doesn't match with your problem.
var list = [];
var raw = {"data":[{"id":"5201521d42"},{"id":"52049e2591"},{"id":"52951699w4"}]};
for(var i=0; i < raw.data.length ; ++i){
list.push(raw.data[i].id);
}
Use the map function on your Array:
data.map(function(item) { return item.id; });
This will return:
["5201521d42", "52049e2591", "52951699w4"]
What is map? It's a method that creates a new array using the results of the provided function. Read all about it: map - MDN Docs
The simplest way to clean any ARRAY in javascript
its using a loop for over the data or manually, like this:
let data = {"data":[{"id":"5201521d42"},{"id":"52049e2591"},
{"id":"52951699w4"}]};
let n = [data.data[0].id,data.data[1].id, data.data[2].id];
console.log(n)
output:
(3) ["5201521d42", "52049e2591", "52951699w4"]
Easy and a clean way to do this.
oldArr = {"data":[{"id":"5201521d42"},{"id":"52049e2591"},{"id":"52951699w4"}]}
oldArr = oldArr["data"].map(element => element.id)
Output: ['5201521d42', '52049e2591', '52951699w4']

fastest way to loop through an array

I want to return an array when one of the elements matches an item within an array.
Is the below code the fastest way to loop through an array when a value matches in a javascript array of arrays?
Note : Welcome any suggestions to modify the variable relatedVideosArray to make it a different data structure for better performance.
var relatedVideosArray = [
["1047694110001"],
["1047694111001", "1019385098001","1020367665001","1020367662001", "1019385097001", "1020367667001"],
["1040885813001"],
["1019385094001", "1019385096001"],
["952541791001", "952544511001", "952544512001", "952544508001", "952541790001","952580933001", "952580934001", "1051906367001"]
]
function getRelatedVideos(videoClicked){
var tempStoreArray = [];
var getCurrentId = videoClicked;
var relVideoslen = relatedVideosArray.length;
for(var i in relatedVideosArray) {
tempStoreArray = relatedVideosArray[i];
for(var j in tempStoreArray){
if(tempStoreArray[j] == getCurrentId){
return relatedVideosArray[i];
}
}
}
}
Update: I initially thought of making a key of video ids and values as all the related ids, but I want to display the key as well as all the related ids if any of the ids within the value array are clicked. Hope this helps to explain the constraint I have.
Modern day browsers support Array indexOf.
For the people saying the array indexOf is slower, basic tests on speed.
var values = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20];
console.time("for");
for(var i=0;i<1000;i++){
for(var j=0;j<=values.length;j++){
if(values[j]===20) break;
}
}
console.timeEnd("for");
console.time("reverse for");
for(i=0;i<1000;i++){
for(var j=values.length-1;j>=0;j--){
if(values[j]===1) break;
}
}
console.timeEnd("reverse for");
console.time("while");
for(i=0;i<1000;i++){
var j=0;
while (j<values.length){
if(values[j]===20) break;
j++;
}
}
console.timeEnd("while");
console.time("reverse while");
for(i=0;i<1000;i++){
var j=values.length-1;
while (j>=0){
if(values[j]===1) break;
j--;
}
}
console.timeEnd("reverse while");
console.time("indexOf");
for(var i=0;i<1000;i++){
var x = values.indexOf(20);
}
console.timeEnd("indexOf");
console.time("toString reg exp");
for(var i=0;i<1000;i++){
var x = (/(,|^)20(,|$)/).test(values.toString);
}
console.timeEnd("toString reg exp");
Two possible solutions:
var relatedVideosArray = [
["1047694110001"],
["1047694111001", "1019385098001","1020367665001","1020367662001", "1019385097001", "1020367667001"],
["1040885813001"],
["1019385094001", "1019385096001"],
["952541791001", "952544511001", "952544512001", "952544508001", "952541790001","952580933001", "952580934001", "1051906367001"]
]
//var getCurrentId = "1019385098001";
var getCurrentId = "1040885813001";
console.time("indexOf");
var tempStoreArray = [];
for(var i = relatedVideosArray.length-1; i>=0; i--){
var subArr = relatedVideosArray[i];
if(subArr.indexOf(getCurrentId)!==-1){
tempStoreArray.push(subArr);
}
}
console.timeEnd("indexOf");
console.log(tempStoreArray);
console.time("toString reg exp");
var tempStoreArray = [];
var re = new RegExp("(,|^)" + getCurrentId + "(,|$)");
for(var i = relatedVideosArray.length-1; i>=0; i--){
var subArr = relatedVideosArray[i];
if(re.test(subArr.toString())){
tempStoreArray.push(subArr);
}
}
console.timeEnd("toString reg exp");
console.log(tempStoreArray);
I believe so if you keep your current structure. Unless you have a way of 'flattening' the array first, so that rather than being nested, there is simply one array with all the values. If this is out of your control or impractical, then you have no other choice than to iterate over every element and its elements.
Otherwise, would you be able to add the values to a map? The current video id would be the key, and the value would be the list of related videos.
If you have control over the data structure then I highly recommend changing it to something more amenable to the type of searches you are performing. First thing that comes to mind is an array of associative arrays. Each of your video arrays would be keyed with the video id ( set the value to anything you want ). That would make your search O(n), where n = the total number of video lists you have.
I'll post some code for this when I get in front of the computer.

How to separate the values from two dimension array in js?

jQuery.get("ChkNewRspLive.php?lastmsgID=" + n, function(newitems){
//some code to separate values of 2d array.
$('#div1').append(msgid);
$('#div2').append(rspid);
});
Let's say the value of newitems is [["320","23"],["310","26"]]
I want to assign "320" and "310" to var msgid.
I want to assign "23" and "26" to var rspid.
How to do that?
I tried to display newitems and the output is "Array". I tried to display newitems[0] and the output is blank.
If I redeclare var newitems = [["320","23"],["310","26"]]; it works. So I guess the variable newitems from jQuery.get is something wrong. Is it I cannot pass the array from other page to current page through jQuery directly?
Regarding the array on other page, if echo json_encode($Arraytest); the output is [["320","23"],["310","26"]] but if echo $Arraytest; the output is Array. How do I pass the array from other page to currently page by jQuery.get?
I don't totally understand the question but I'm going to assume you want the values in an array, as two values can't be stored in one (scalar) variable simultaneously.
jQuery.get("ChkNewRspLive.php?lastmsgID=" + n, function(newitems){
//some code to separate values of 2d array.
var msgid = [],
rspid = [];
for( i = 0 ; i < newitems.length ; i++){
msgid[msgid.length] = newitems[i][0];
rspid[rspid.length] = newitems[i][1];
}
//msgid now contains ["320","310"]
//rspid now contains ["23","26"]
});
Bear in mind those are in the function scope. If you want to use them outside of that scope instantiate them outside. see: closure
You can use pluck from underscore.js: http://documentcloud.github.com/underscore/#pluck
var msgid = _(newitems).pluck(0)
var rspid = _(newitems).pluck(1)
Try this:
function getArrayDimension(arr, dim) {
var res = [];
for(var i = 0; i < arr.length; i++) {
res.push(arr[i][dim]);
}
return res;
}
var newitems = [["320","23"],["310","26"]];
var msgid = getArrayDimension(newitems, 0);
var rspid = getArrayDimension(newitems, 1);
msgid and rspid are arrays holding the 'nth' dimention.
Tnx

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