I am using leaflet 1.7.1 and successfully loaded JSON file from the local memory of my machine.
I have an object which looks like this:
covid = {"AFG":{"continent":"Asia","location":"Afghanistan","population":38928341.0,"population_density":54.422,"median_age":18.6},
"KOR":{"continent":"Asia","location":"Afghanistan","population":38928341.0,"population_density":54.422,"median_age":18.6},
"KGZ":{"continent":"Asia","location":"Afghanistan","population":38928341.0,"population_density":54.422,"median_age":18.6},
....}
What I want to do is to get countries by their ISO country code(e.g. KOR, KGZ etc).
Even after converting to object file I cannot get by index like covid[0] but it is not working.
I am new to JS and cannot really handle the data.
Notice it's not called JavaScript Array Notation, but rather JavaScript Object Notation.
The problem: covid is NOT an array. It's an object. Here's a great read. To fix your problem, you refer to the actual name.
To use it in your project, you could loop through the object and use it like so:
for (let isoCountryName in covid) {
console.log(`${isoCountryName}`);
}
Here's a demo:
var covid = {"AFG":{"continent":"Asia","location":"Afghanistan","population":38928341.0,"population_density":54.422,"median_age":18.6},
"KOR":{"continent":"Asia","location":"Afghanistan","population":38928341.0,"population_density":54.422,"median_age":18.6},
"KGZ":{"continent":"Asia","location":"Afghanistan","population":38928341.0,"population_density":54.422,"median_age":18.6}};
for (let isoCountryName in covid) {
console.log(`ISO country name: ${isoCountryName}`);
}
Related
I've been trying to load certain Json with Ajax GET request and then parsing it.
However when trying to access the Json key from HTML script tag it was undefined.
In order to debug this issue, I logged all the keys of Json in console as well as the Json itself. Therefore i utilized this function:
function getInv() {
$.get( "/inventory/", function( data ) {
var invList = data.split(",, "); // Explanation is below
console.log(invList[0]) // Just testing with first object
console.log(Object.keys(invList[0]));
});
}
getInv();
Purpose of data.split(",, "):
Since my backend script uses different programming language, I had to interpret it to the one suitable for Javascript.
There also were multiple Json objects, So i separated them with ",, " and then split them in Javascript in order to create a list of Json objects.
After calling the function, Following output was present:
Although the interesting part is that after pasting Json object in console like this:
This was the output:
So basically, in script tag, i was unable to access object's keys, although once i used it manually in console, all keys could be accessed.
What could be the purpose behind this? It seems quite strange that different outputs are given. Perhaps invList[0] is not Json object at all in the script tag? Thanks!
data.split() returns an array of strings, not objects. You need to use JSON.parse() to parse the JSON string to the corresponding objects.
function getInv() {
$.get( "/inventory/", function( data ) {
var invList = data.split(",, ");
console.log(invList[0]) // Just testing with first object
var obj = JSON.parse(invList[0]);
console.log(Object.keys(obj));
});
}
You can use .map() to parse all of them, then you'll get an array of objects like you were expecting:
var invList = data.split(",, ").map(JSON.parse);
I have a variable called uids
var uids = [];
Then I write some value to it property
uids[16778923] = "3fd6335d-b0e4-4d77-b304-d30c651ed509"
But before it
if (!uids[user.id]) {
uids[user.id] = generateKey(user);
}
This thing behaves ok. If I try to get the value of it property
uids[currentUser.id]
It will give me a value of this property. If I try to call some methods like
Object.keys(uids);
It will give me, what I expected. And here the mystery comes...
uids;
RAM rest in piece. See the node eating ram
I am very confused now. What's wrong?
This is because you are creating a huge array and node will reserve memory for it - who knows what comes. I'd say that's a scenario where you would use a Map (or a plain object, but Map feels better here.
var uids = new Map();
var key = 456464564564654;
if (! uids.has(key)) {
uids.set(key, generateKey(user))
}
You are creating an empty array (length is zero), then you assign some value to an arbitrary index. This will make the array grow as big as the index and assign the value to that index. Look at this example using node.js REPL:
> var a = []
undefined
> a[5] = "something"
'something'
> a
[ , , , , , 'something' ]
> a.length
6
Instead of creating an array, you could create a Map() or an common javascript object (singleton). Javascript objects behave like Maps but only Strings can be used as keys. If you assign a Number to be key, javascript will convert it to String automatically.
Personally, I would go with objects because they perform better. Instantiating an object takes longer than instantiating a Map (and it doesn't seem like you need to create several groups of "uids"), but once done, adding new keys and retrieving values from any key in faster when using common objects. At least that's how things go in my node.js v6.7.0 on ubuntu 14.04 but you could try for yourself. And it would also make the least alteration to your code.
var uids = {} // common/ordinary empty javascript object instead of array.
if (!uids[user.id]) { // getting value from one key works the same.
uids[user.id] = generateKey(user) // assignment works the same.
}
////
uids[16778923] = "3fd6335d-b0e4-4d77-b304-d30c651ed509" // key will be "16778923".
uids[16778923] // getting value for key "16778923" can be done using 16778923 instead of "16778923".
////
uids[currentUser.id] // still returning values like this.
Object.keys(uids) // still returning an array of keys like this. but they are all Strings.
I'm working on a project with search option filters and they're updated via sessions, but I'm having some issues with the session variable actually taking the array. It works fine for non-array based values, but for instance when I pass an array with RegExp objects to be used in a mongo $in selector it doesn't work as expected. The functions work fine right up until it hits Session.set() in the code snippet below so I know I have to be doing something wrong with that:
Option.prototype.update = function () {
//updates session variable if static option
if (!this.isDynamic) {
if(Object.prototype.toString.call(this.value) === '[object Array]') {
var temp = this.value.slice(0);
Session.set(this.optionName, temp);
console.log(Session.get(this.optionName));
}
else {
Session.set(this.optionName, this.value);
}
};
};
for whatever reason instead of displaying the array with values in it, it displays
[Object], and the object in that array is empty. I've read the other Overflow posts on Session variables and arrays, and simply cloning the array before passing it doesn't seem to be working. Any idea what I'm doing wrong?
Your code is correct (although slightly convoluted). The problem is that Session only takes EJSON–able values, and regexes are not EJSON–able. From the perspective of EJSON, regex looks just like an empty object, and that's exactly what you get in the stored array. Similar problem would appear if you try to store object with custom prototype, or with private (not enumerable) properties: everything that is not serialized to EJSON is lost.
The solution here is to create your own serialization method that will work with regexes. For example, if you will always have a flat array of regexes, you could simply stringify them before storing:
var temp = _.map(this.value, function(regex) {
return regex.toString();
});
I am working on an app that heavily uses JavaScript. I am attempting to include some object-oriented practices. In this attempt, I have created a basic class like such:
function Item() { this.init(); }
Item.prototype = {
init: function () {
this.data = {
id: 0,
name: "",
description: ""
}
},
save: function() {
alert("Saving...");
$.ajax({
url: getUrl(),
type: "POST",
data: JSON.stringify(this.data),
contentType: "application/json"
});
}
}
I am creating Item instances in my app and then saving them to local storage like such:
Item item = new Item();
window.localStorage.setItem("itemKey", JSON.stringify(item));
On another page, or at another time, I am retriving that item from local storage like such:
var item = window.localStorage.getItem("itemKey");
item = JSON.parse(item);
item.save();
Unfortunately, the "save" function does not seem to get reached. In the console window, there is an error that says:
*save_Click
(anonymous function)
onclick*
I have a hunch that the "(anonymous function)" is the console window's way of saying "calling item.save(), but item is an anonymous type, so I am trying to access an anonymous function". My problem is, I'm not sure how to convert "var item" into an Item class instance again. Can someone please show me?
Short answer:
Functions cannot be serialized into JSON.
Explanation:
JSON is a cross-platform serialization scheme based on a subset of JS literal syntax. This being the case, it can only store certain things. Per http://www.json.org/ :
Objects: An object is an unordered set of name/value pairs. An object begins with { (left brace) and ends with } (right brace). Each name is followed by : (colon) and the name/value pairs are separated by , (comma).
Arrays: An array is an ordered collection of values. An array begins with [ (left bracket) and ends with ] (right bracket). Values are separated by , (comma).
values: A value can be a string in double quotes, or a number, or true or false or null, or an object or an array. These structures can be nested.
Functions cannot be serialized into JSON because another non-JS platform would not be able to unserialize and use it. Consider the example in reverse. Say I had a PHP object at my server which contained properties and methods. If I serialized that object with PHP's json_encode() and methods were included in the output, how would my JavaScript ever be able to parse and understand PHP code in the methods, let alone use those methods?
What you are seeing in your resulting JSON is the toString() value of the function on the platform you're using. The JSON serilizer calls toString() on anything being serialized which isn't proper for JSON.
I believe your solution is to stop storing instances in JSON/local storage. Rather, save pertinent data for an instance which you set back to a new instance when you need.
I know this question is answered already, however I stumbled upon this by accident and wanted to share a solution to this problem, if anyone is interested.
instead of doing this:
var item = window.localStorage.getItem("itemKey");
item = JSON.parse(item);
item.save();
do something like this:
// get serialized JSON
var itemData = window.localStorage.getItem("itemKey");
//instantiate new Item object
var item = new Item();
// extend item with data
$.extend(item, JSON.parse(itemData));
// this should now work
item.save();
this will work so long as the function you are wanting to call (ie, save()) is prototypal and not an instance method (often times the case, and is indeed the case in the OP's original question.
the $.extend method is a utility method of jquery, but it is trivial to roll your own.
You cant do that, how can javascript possibly knows that item have a save function ? json doesnt allow functions as datas. just read the json spec , you cant save functions.
what you need to do is to create a serialize and deserialize method in the hash you want to stock. that will specifiy what to export and how you can "wake up" an object after parsing the corresponding json string.
You can only store plain Objects in DOMstorages (cookies, urlparams..., everything that needs [de]serialisation through JSON.stringify/JSON.parse). So what you did when sending the ajax data
ajaxsend(this.data);
also applies to string serialisation. You can only store the data, not the instance attributes (like prototype, constructor etc.). So use
savestring(JSON.stringify(item.data));
which is possible because item.data is such a plain Object. And when restoring it, you will only get that plain data Object back. In your case it's easy to reconstruct a Item instance from plain data, because your Items hold their values (only) in a public available property:
var item = new Item;
item.data = JSON.parse(getjsonstring());
Disclaimer
Not a full time time J.S. Developer, answer may have some minor bugs:
Long Boring Explanation
As mentioned by #JAAulde, your object cannot be serialized into JSON, because has functions, the technique that you are using doesn't allow it.
Many people forget or ignore that the objects that are used in an application, may not be exactly the same as saved / restored from storage.
Short & quick Answer
Since you already encapsulate the data members of your object into a single field,
you may want to try something like this:
// create J.S. object from prototype
Item item = new Item();
// assign values as you app. logic requires
item.data.name = "John Doe";
item.data.description = "Cool developer, office ladies, love him";
// encoded item into a JSON style string, not stored yet
var encodedItem = JSON.stringify(item.data)
// store string as a JSON string
window.localStorage.setItem("itemKey", encodedItem);
// do several stuff
// recover item from storage as JSON encoded string
var encodedItem = window.localStorage.getItem("itemKey");
// transform into J.S. object
item.data = JSON.parse(encodedItem);
// do other stuff
Cheers.
I am trying to use the following code to create a list of client names from some json returned from an Ajax call.
The data is as follows:
{"status":1,"data":{"clients":[{"ClientID":"1","AccountID":"1","ClientName":"Access Loan Mitigation","Active":"1"},{"ClientID":"2","AccountID":"1","ClientName":"Big Time Business","Active":"1"},{"ClientID":"3","AccountID":"1","ClientName":"Bill Releford","Active":"1"},{"ClientID":"4","AccountID":"1","ClientName":"Bonnie Silverman","Active":"1"},{"ClientID":"5","AccountID":"1","ClientName":"Dear Holdings","Active":"1"},{"ClientID":"6","AccountID":"1","ClientName":"Calm Dental","Active":"1"},{"ClientID":"7","AccountID":"1","ClientName":"Eva Field","Active":"1"},{"ClientID":"8","AccountID":"1","ClientName":"First Independent Pictures","Active":"1"},{"ClientID":"9","AccountID":"1","ClientName":"Gallery 825","Active":"1"},{"ClientID":"10","AccountID":"1","ClientName":"Greenway Arts Alliance","Active":"1"},{"ClientID":"11","AccountID":"1","ClientName":"International Strategy Group","Active":"1"},{"ClientID":"12","AccountID":"1","ClientName":"Ramtin","Active":"1"},{"ClientID":"13","AccountID":"1","ClientName":"Spabro","Active":"1"},{"ClientID":"14","AccountID":"1","ClientName":"LMGA","Active":"1"},{"ClientID":"15","AccountID":"1","ClientName":"Main Street Business Association","Active":"1"},{"ClientID":"16","AccountID":"1","ClientName":"Rabbit Animation","Active":"1"},{"ClientID":"17","AccountID":"1","ClientName":"Rooms & Gardens","Active":"1"},{"ClientID":"18","AccountID":"1","ClientName":"Summertime","Active":"1"},{"ClientID":"19","AccountID":"1","ClientName":"Sue Shellock","Active":"1"},{"ClientID":"20","AccountID":"1","ClientName":"Susan Gates","Active":"1"},{"ClientID":"21","AccountID":"1","ClientName":"The Park Entertainment","Active":"1"},{"ClientID":"22","AccountID":"1","ClientName":"Unified Dispatch","Active":"1"},{"ClientID":"23","AccountID":"1","ClientName":"Westside Media Group","Active":"1"},{"ClientID":"24","AccountID":"1","ClientName":"YHD","Active":"1"},{"ClientID":"25","AccountID":"1","ClientName":"Discoverfire, Inc.","Active":"1"}]}}
and the code is like so:
for (var Client in o.data.clients) {
$('#list_container').append("<div>"+Client.ClientName+"</div>");
}
Not quite working, and I've tried a few different ways of accessing the ClientName property. Javascript isn't my strongest language, and getting data out of objects just kills me - used to PHP object and arrays.
I'm sure this is simple - can somebody show the right syntax?
Thanks!
Clients is an array so it's better to use jQuery's each on it:
$.each( o.data,clients, function(idx, client) {
// use client.ClientName here
});
That's not quite how the for loop works. An easier, more accurate, and more reliable way to tackle this is to use the traditional for syntax like so:
for (var i = 0; i < o.data.clients.length; i++) {
var client = o.data.clients[i];
$('#list_container').append("<div>"+client.ClientName+"</div>");
}
The for syntax you were using will work, but it's still iterating over indices (not values), and even then it's not limited to just the integer indices in the array — it could also include other properties defined on the array prototype, or even on the particular array object. Iterating using the boring i = 0 syntax is a far better option for traditional arrays like this.