I have an array of data get from the server(ordered by date):
[ {date:"2012-8", name:"Tokyo"}, {date:"2012-3", name:"Beijing"}, {date:"2011-10", name:"New York"} ]
I'd like to :
get the name of the first element whose date is in a given year, for example, given 2012, I need Tokyo
get the year of a given name
change the date of a name
which data structure should I use to make this effective ?
because the array could be large, I prefer not to loop the array to find something
Since it appears that the data is probably already sorted by descending date you could use a binary search on that data to avoid performing a full linear scan.
To handle the unstated requirement that changing the date will then change the ordering, you would need to perform two searches, which as above could be binary searches. Having found the current index, and the index where it's supposed to be, you can use two calls to Array.splice() to move the element from one place in the array to another.
To handle searches by name, and assuming that each name is unique, you should create a secondary structure that maps from names to elements:
var map = {};
for (var i = 0, n = array.length; i < n; ++i) {
var name = array[i].name;
map[name] = array[i];
}
You can then use the map array to directly address requirements 2 and 3.
Because the map elements are actually just references to the array elements, changes to those elements will happen in both.
Assuming you are using unique cities, I would use the city names as a map key:
cities = {
Tokyo: {
date: "2012-8"
},
New York: {
date: "2011-10"
}
}
To search by date:
function byDate(date) {
for(el in cities) {
if(cities.hasOwnProperty(el) && cities[el].date === date)
return el;
}
}
Just for the record: without redesigning your date structure you could use sorting combined with the Array filter or map method:
function sortByDate(a,b){
return Number(a.date.replace(/[^\d]+/g,'')) >
Number(b.date.replace(/[^\d]+/g,''));
}
var example = [ {date:"2012-8", name:"Tokyo"},
{date:"2012-3", name:"Beijing"},
{date:"2011-10", name:"New York"} ]
.sort(sortByDate);
//first city with year 2012 (and the lowest month of that year)
var b = example.filter(function(a){return +(a.date.substr(0,4)) === 2012})[0];
b.name; //=> Beijing
//year of a given city
var city = 'Tokyo';
var c = example.filter(function(a){return a.city === city;})[0];
c.year; //=> 2012
//change year of 'New York', and resort data
var city = 'New York', date = '2010-10';
example = example.map(
function(a){if (a.name === city) {a.date = date;} return a;}
).sort(sortByDate);
Related
This is the URL from GeoServer to get feature info
{"type":"FeatureCollection","features":[{"type":"Feature","id":"weather_warning_day_1.fid--418ec0da_178b69d5dfc_-715c","geometry":null,"properties":{"issue_date":"2021-04-09","updated_at":"2021-04-09T09:26:33+05:30","utc_time":0,"state_name":"Odisha","state_id":21,"district_name":"MAYURBHANJ","district_id":232,"api_district_name":"MAYURBHANJ","day_1":"6,9,10","day1_color":3}}],"totalFeatures":"unknown","numberReturned":1,"timeStamp":"2021-04-09T15:38:19.536Z","crs":null}
the data I want to extract is of variable: "day_1":"6,9,10"
which I got from the layer and stored it in the variable as
var warning_day_1 = weather_warning_layer_data.features[0].properties.day_1
so basically the input is "day_1":"6,9,10"
which I have stored in the array as
[{"warning":"6"},{"warning":"9"},{"warning":"10"}]
and corresponding output should be Dust Storm, Heat Wave, Hot Day
Dust Storm, Heat Wave, Hot Day
or if the input was "day_1":"2,5"
then output should have been Heavy Rain, Hailstorm
or if the input was "day_1":"1"
then output should have been No Warning
After reading the data of the string and creating its array, I have to compare it with another array and extract the key values (display) corresponding to the key values (warning) in the 1st array.
var warning_data_split = warning_day_1.split(/[ ,]+/);
var warning_data_from_api_array = new Array;
warning_data_from_api_array.push(warning_data_split);
for (var i = 0; i < warning_data_from_api_array.length; i++) {
var item_in_array_to_compare = warning_data_from_api_array[i];
if(warning_data_from_api_array[item_in_array_to_compare.warning_data_from_api_array])
{warning_data_from_api_array[item_in_array_to_compare.warning_data_from_api_array].push(item_in_array_to_compare);}
else {
warning_data_from_api_array[item_in_array_to_compare.warning_data_from_api_array] = [item_in_array_to_compare];}}
let final_array_to_compare = item_in_array_to_compare
final_array_to_compare = final_array_to_compare.map(x => ({warning: x}));
/// this is the first array ////////////
The values in this array are not static in length, as it keeps on changing like, sometimes the array has value [1] or [1,2], [2,5,8], [4,7,12], etc
so I have to extract the corresponding values of display from the lookup array given below
var warning_code_meaning_list = [
{ warning:"1", display:"No Warning"},
{ warning:"2", display:"Heavy Rain"},
{ warning:"3", display:"Heavy Snow"},
{ warning:"4", display:"Thunderstorm & Lightning, Squall etc"},
{ warning:"5", display:"Hailstorm"},
{ warning:"6", display:"Dust Storm"},
{ warning:"7", display:"Dust Raising Winds"},
{ warning:"8", display:"Strong Surface Winds"},
{ warning:"9", display:"Heat Wave"},
{ warning:"10", display:"Hot Day"},
{ warning:"11", display:"Warm Night"},
{ warning:"12", display:"Cold Wave"},
{ warning:"13", display:"Cold Day"},
{ warning:"14", display:"Ground Frost"},
{ warning:"15", display:"Fog"}
]
The data which I am getting in warning_day_1 (in the very first line of the code) is a string (this couldn’t be saved as float/integer in the database column because sometimes there are more than 1 warning for a specific place, so I have stored this as a text in the database)
Which I’m converting to an array after reading it from the API
Now this string, which I am fetching from API has variable data,
Some time single digit like: 1
Sometime multiple : 1,2,3
And each of the integer present in this array corresponds to the specific text shown in the next array like if the warning is 2 it means the heavy rainfall,
but if the string (later converted to an array, with “warning” as a key) has 2,5 as value, it means: heavy rainfall & Hailstorm
I want that the values which come up in array 1 (the dynamic one) got match with the 2nd array ( a sort of lookup array) and fetch its display value as output.
How to do so?
You could use an object to map your warnings to messages.
Try this:
const data = {"type":"FeatureCollection","features":[{"type":"Feature","id":"weather_warning_day_1.fid--418ec0da_178b69d5dfc_-715c","geometry":null,"properties":{"issue_date":"2021-04-09","updated_at":"2021-04-09T09:26:33+05:30","utc_time":0,"state_name":"Odisha","state_id":21,"district_name":"MAYURBHANJ","district_id":232,"api_district_name":"MAYURBHANJ","day_1":"6,9,10","day1_color":3}}],"totalFeatures":"unknown","numberReturned":1,"timeStamp":"2021-04-09T15:38:19.536Z","crs":null}
var warning_code_meaning_list = {
"1":"No Warning",
"2":"Heavy Rain",
"3":"Heavy Snow",
"4":"Thunderstorm & Lightning, Squall etc",
"5":"Hailstorm",
"6":"Dust Storm",
"7":"Dust Raising Winds",
"8":"Strong Surface Winds",
"9":"Heat Wave",
"10":"Hot Day",
"11":"Warm Night",
"12":"Cold Wave",
"13":"Cold Day",
"14":"Ground Frost",
"15":"Fog",
};
results = data["features"].map(feature => {
return feature.properties.day_1.split(',').map(code => {
return warning_code_meaning_list[code];
});
});
That gives you an array of arrays of the displays:
[ [ 'Dust Storm', 'Heat Wave', 'Hot Day' ] ]
I'm brand new to programming so I apologize if this is a simple question.
I had a unique practice problem that I'm not quite sure how to solve:
I'm dealing with two arrays, both arrays are pulled from HTML elements on the page, one array is representing a bunch of states, and the next array is representing their populations. The point of the problem is to print the name of the states and their less than average populations.
To find and print all of the populations that are less than the average I used this code:
function code6() {
// clears screen.
clr();
// both variables pull data from HTML elements with functions.
var pop = getData2();
var states = getData();
var sum = 0;
for( var i = 0; i < pop.length; i++ ){
sum += parseInt( pop[i], 10 );
var avg = sum/pop.length;
if (pop[i] < avg) {
println(pop[i]);
// other functions used in the code to get data, print, and clear the screen.
function getData() {
var dataSource = getElement("states");
var numberArray = dataSource.value.split('\n');
// Nothing to split returns ['']
if (numberArray[0].length > 0) {
return(numberArray);
} else {
return [];
}
}
// Get the data from second data column
function getData2() {
var dataSource = getElement("pops");
var numberArray = dataSource.value.split('\n');
// Nothing to split returns ['']
if (numberArray[0].length > 0) {
return(numberArray);
} else {
return [];
}
}
// Clear the 'output' text area
function clr() {
var out = getElement("output");
out.value = "";
}
// Print to the 'output' HTML element and ADDS the line break
function println(x) {
if (arguments.length === 0) x = '';
print(x + '\n');
}
Now I just need to know how to get the value of these positions within the array so I can pull out the same positions from my states array and display them both side by side. Both arrays have the identical amount of items.
I hope this makes sense and thanks in advance to anyone who has time to take a look at this.
Best regards,
-E
Its a little hard to tell what you are trying to accomplish, but I guess you are going for something like:
'use strict'
function code6() {
const populations = ['39000000', '28000000', '21000000'];
const stateNames = ['california', 'texas', 'florida'];
const states = populations.map((population, i) => ({
'name': stateNames[i],
'population': Number(population),
}));
const sum = states.reduce((sum, state) => sum + state.population, 0);
const average = sum / populations.length;
states
.filter(state => state.population < average)
.forEach(state => {
const name = state.name;
const population = state.population;
console.log(`state name: ${name}, population: ${population}`);
});
}
// run the code
code6();
// state name: texas, population: 28000000
// state name: florida, population: 21000000
I took the liberty of refactoring your code to be a little more modern (es6) and Idiomatic. I hope its not to confusing for you. Feel free to ask any questions about it.
In short you should use:
'use strict' at the top of your files
const/let
use map/filter/forEach/reduce to iterate lists.
use meaningfull names
, and you should avoid:
classic indexed for-loop
parseInt
, and pretty much never ever use:
var
If your states array is built with corresponding indices to your pop one, like this:
states; //=> ['Alabama', 'Alaska', 'Arizona', ...]
pop; //=> [4863300, 741894, 6931071, ...]
then you could simply update your print statement to take that into account:
if (pop[i] < avg) {
println(state[i] + ': ' + pop[i]);
}
Or some such.
However, working with shared indices can be a very fragile way to use data. Could you rethink your getData and getData2 functions and combine them into one that returns a structure more like this the following?
states; //=> [
// {name: 'Alabama', pop: 4863300}
// {name: 'Alaska', pop: 741894},
// {name: 'Arizona', pop: 6931071},
// ...]
This would entail changes to the code above to work with the pop property of these objects, but it's probably more robust.
If your pop and state looks like:
var state = ['state1', 'state2', ...];
var pop = ['state1 pop', 'state2 pop', ...];
Then first of all, avg is already wrong. sum's value is running along with the loop turning avg's formula into sum as of iteration / array length instead of sum of all pops / array length. You should calculate the average beforehand. array.reduce will be your friend.
var average = pop.reduce(function(sum, val){return sum + val;}, 0) / pop.length;
Now for your filter operation, you can:
Zip up both arrays to one array using array.map.
Filter the resulting array with array.filter.
Finally, loop through the resulting array using array.forEach
Here's sample code:
var states = ['Alabama', 'Alaska'];
var pop = [4863300, 741894];
var average = pop.reduce(function(sum, val){return sum + val;}) / pop.length;
console.log('Average: ' + average);
states.map(function(state, index) {
// Convert 2 arrays to an array of objects representing state info
return { name: state, population: pop[index] };
}).filter(function(stateInfo) {
console.log(stateInfo);
// Filter each item by returning true on items you want to include
return stateInfo.population < average;
}).forEach(function(stateInfo) {
// Lastly, loop through your results
console.log(stateInfo.name + ' has ' + stateInfo.population + ' people');
});
I have 2 Arrays and one is 2 dimensional and another is 1 dimensional. I need to compare both and need to store there common data in another array. I tried the below approach:-
tw.local.listtodisplayNW = new tw.object.listOf.listtodisplayNWBO();
//if(tw.local.SQLResults[0].rows.listLength >
// tw.local.virtualServers.listLength)
var k=0;
for (var i=0;i<tw.local.SQLResults[0].rows.listLength;i++)
{
log.info("Inside SQLResults loop - For RuntimeID: "
+tw.local.SQLResults[0].rows[i].data[3]);
for(var j=0;j<tw.local.virtualServers.listLength;j++)
{
log.info("Inside API loop - For RuntimeID: "
+tw.local.virtualServers[j].runtimeid);
if(tw.local.SQLResults[0].rows[i].data[3] ==
tw.local.virtualServers[j].runtimeid)
{
tw.local.listtodisplayNW[k] = new tw.object.listtodisplayNWBO();
tw.local.listtodisplayNW[k].vsysName =
tw.local.virtualServers[j].virtualSystemName;
tw.local.listtodisplayNW[k].vsysID =
tw.local.virtualServers[j].virtualSystemId;
tw.local.listtodisplayNW[k].serverName =
tw.local.virtualServers[j].serverName;
tw.local.listtodisplayNW[k].serverID =
tw.local.virtualServers[j].serverId;
tw.local.listtodisplayNW[k].runtimeID =
tw.local.virtualServers[j].runtimeid;
//tw.local.listtodisplayNW[k].IPAddress =
tw.local.virtualServers[j].nics[j].ipAddress;
log.info("VsysName:
"+tw.local.listtodisplayNW[k].vsysName+"RuntimeID:
"+tw.local.listtodisplayNW[k].runtimeID);
//tw.local.listtodisplayNW[k] = new
tw.object.listtodisplayNWBO();
tw.local.listtodisplayNW[k].currentSpeed =
tw.local.SQLResults[0].rows[i].data[5];
log.info("VsysName:
"+tw.local.listtodisplayNW[k].vsysName+"RuntimeID:
"+tw.local.listtodisplayNW[k].runtimeID+"CurrentSpeed:
"+tw.local.listtodisplayNW[k].currentSpeed);
if(tw.local.listtodisplayNW[k].currentSpeed != "100 Mbps")
{
tw.local.listtodisplayNW[k].desiredSpeed = "100 Mbps";
}
else
{
tw.local.listtodisplayNW[k].desiredSpeed = "1 Gbps";
}
log.info("DesiredSpeed:
"+tw.local.listtodisplayNW[k].desiredSpeed);
k++;
}
}
log.info("Length of
listtodisplayNW"+tw.local.listtodisplayNW.listLength);
}
In above code SQLResults is a 2-d array and virtualServers is a 1-D array.
I need to compare both these array and common data need to be store in another array. Here performance is not good. Is there any other way to do this efficiently. Please make a needful favour and Thanks in advance.
Assuming integer data, the following example works on the theme of array implementation of set intersection, which will take care of performance.
Convert 2D array to 1D.
var 2DtoIDArray = 2DArray.join().split(",");
Create an array named marker whose purpose is to serve as a lookup that element.
This needs to be done as follows.
Iterate through the smaller array, say 1DArray and keep setting marker as follows throughout iteration.
marker[1DArray[counter]]='S1';
Now iterate through 2Dto1DArray array(you may use nested loop iteration if you dont want to convert it to 1 dimesnional) and for each element
of this array check if its marked as 'S1' in the marker lookup array.
If yes, keep adding the elements in the commonElementsArray.
Follow this simple approach
Since the matching condition is only one between the two large arrays, create two maps (one for each array) to map each record against that attribute which is to be matched
For SQLResults
var map1 = {};
tw.local.SQLResults[0].rows.each( function(row){
map1[ row.data[3] ] = row;
});
and similarly for virtual servers
var map2 = {};
tw.local.virtualServers.each( function(vs){
map2[ vs.runtimeid ] = vs;
});
Now iterate these two maps wrt to their keys and set the values in new array
new array being tw.local.listtodisplayNW
tw.local.listtodisplayNW = [];
Object.keys( map1 ).forEach( function( key ){
if( map2[ key ] )
{
//set the values in tw.local.listtodisplayNW
}
})
Complexity of the approach is simply O(n) since there is no nested loops.
When I do this I get an array which stores the data as grouped by the month and day of the date but not by the year (I am doing this to get maximum, minimum, and average values for each day there is data for)
The problem is that the array stores an array of 2-3 values for that day and month within the date which is the key value. Those 2-3 indices each have an array of length one that holds a reference to an object which has the actual data point (level) I need. The object contains three attributes, date, id (which is always null), and level which is a float.
I either need to find a way so those 2-3 indices hold the object directly, or find a way that _.each can access the level.
Any thoughts?
var groupedData = _.groupBy(data, "date");
var groupedLevels = _.groupBy(groupedData, function (points, date) {
var dateParsed = parseDate(date);
var month = dateParsed.getMonth();
var day = dateParsed.getDate();
var monthDay = month + "-" + day;
return monthDay;
});
_.each(groupedLevels, function (points, date) {
var levels = _.map(_.pluck(points, "level"), parseFloat);
minimum.push([ date, R.min(levels) ]);
maximum.push([ date, R.max(levels);
var averageLevel = R.sum(levels) / levels.length;
average.push([date, averageLevel]);
})
So the data, as is, which is the original input looks like this (a sample piece):
[ { date: "2009-01-01",
id: null,
level: "0.08",
},
// ...
]
Currently, groupedData is this:
{ "2009-01-01":
[ { date: "2009-01-01",
id: null,
level: "0.08"
}
],
// ...
}
groupedLevels looks like this, for example:
{ "0-1":
[ [ { date: "2009-01-01".
id: null,
level: "0.08"
}
],
// ...
],
// ...
}
I want to skip having all the arrays of length one and just have the object stored there.
I think you can fix the immediate issue by replacing this line:
var levels = _.map(_.pluck(points, "level"), parseFloat);
With this:
var levels = _.map(_.pluck(points[0], "level"), parseFloat);
...but I think the real problem might be that you're doing groupBy twice when you don't need to. This single groupBy ought to be equivalent, but without the extra nested array:
var groupedLevels = _.groupBy(data, function(item) {
var dateParsed = parseDate(item.date);
var month = dateParsed.getMonth();
var day = dateParsed.getDate();
return month + '-' + day;
});
With this, your each should work as expected.
[
{"task":"test","created":"/Date(1291676980607)/"},
{"task":"One More Big Test","created":"/Date(1291677246057)/"},
{"task":"New Task","created":"/Date(1291747764564)/"}
]
I looked on here, and someone had the same sort of question, but the "checked" correct answer was that it will be different on IE if the item is deleted, which would be fine. My issue is, those items above are stored, but when i go and grab them, iterate, and return, the items are reversed and the created is at the 0 index and task is at 1. Also, i need to return this as JSON.
Here is my basic JS (value == an int the user is passing in):
outputJSON = {};
for(x in json[value]){
outputJSON[x] = _objectRevival(json[value][x]);
}
return outputJSON;
That returns:
created: Mon Dec 06 2010 15:09:40 GMT-0800 (Pacific Standard Time)
task: "test"
The order of the properties of an object is undefined. It is not possible to force them in a specified order. If you need them in a specific order, you can build this structure reliably using arrays:
var values = [
[["task", "test"], ["created", "/Date(1291676980607)/"]],
[["task", "One More Big Test"], ["created", "/Date(1291677246057)/"]],
[["task", "New Task"], ["created", "/Date(1291747764564)/"]]
];
Then you can iterate over your structure like this:
for (var i = 0; i < values.length; i++) {
for (var k = 0; k < values[i]; k++) {
// values[i][k][0] contains the label (index 0)
// values[i][k][1] contains the value (index 1)
}
}
To enforce a particular order for your output just replace json[value] in your for loop with an array of the object properties in the order you want to display them, in your case ["task", "created"].
The problem is that javascript objects don't store their properties in a specific order. Arrays on the other do (hence why you can get something consistent from json[0], json[1], json[2]).
If your objects will always have "task" and "created", then you can get at them in any order you want.
json[value]["task"]
and
json[value]["created"]
Update:
This should work with your existing code.
Before sending the json object:
var before = [
{"task":"test","created":"/Date(1291676980607)/"},
{"task":"One More Big Test","created":"/Date(1291677246057)/"},
{"task":"New Task","created":"/Date(1291747764564)/"}
];
var order = [];
for (var name in before[0]) {
order.push(name); // puts "task", then "created" into order (for this example)
}
Then send your json off to the server. Later when you get the data back from the server:
var outputJSON = {};
for (var x in order) {
if (order.hasOwnProperty(x)) {
outputJSON[order[x]] = _objectRevival(json[value][order[x]]); // I'm not sure what _objectRevival is...do you need it?
}
}
return outputJSON;
var items = ["bag", "book", "pen", "car"];
items.reverse();
This will result in the following output:
car , pen, book, bag
Even if you have JSON array it will reverse.