I want to flatten a multi-level object and vice versa.
For example:
{
option1:value1,
option2:value2,
option3:{
key1:value31,
key2:value32
},
option4:[value40,value41,value42]
}
Would be equivalent to:
{
option1:value1,
option2:value2,
"option3.key1":value31,
"option3.key2":value32,
"option4.0":value40,
"option4.1":value41,
"option4.2":value42
}
This is for small objects, the objective of the flattened expression is to facilitate the data collection in a form and the merge with default options. For example I can have form elements like this:
<input name="option4.0" value="value40"/>
Is this a standard approach, or is there a better way? Are there libraries that already do this?
That format ({ option4.2: value42 }) won't work (because the . in the key will be parsed as a dot operator). Instead, you'll need to quote the key:
{ 'option4.2': value42 }
However, this is very non-standard. Flattening objects is typically not required - if you want to submit such an object to a server, you can use JSON to serialize it without flattening:
var stringForServer = JSON.stringify(normalObject);
If you're looking for a library to manipulate objects and arrays etc, underscore is probably your best bet:
http://underscorejs.org/
cheers!
I experimented with my idea, it works fine but has a few limitations.
The obvious ones is that a key cannot contain a dot (dots are delimiters with this technique), and keys cannot be numbers (or else the algorithm interprets it as an array index).
Another issue is that it won't work if a value is an empty object or array (e.g. option4:[]).
Related
Bit of a lengthy one so those of you who like a challenge (or I'm simply not knowledgeable enough - hopefully it's an easy solution!) read on!
(skip to the actual question part to skip the explanation and what I've tried)
Problem
I have a site that has a dataset that contains an object with multiple objects inside. Each of those objects contains an array, and within that array there are multiple objects. (yes this is painful but its from an API and I need to use this dataset without changing or modifying it.) I am trying to filter the dataset based of the key-value pairs in the final object. However, I have multiple filters being executed at once.
Example of Path before looping which retrieves the key-value pair needed for one hall.
["Hamilton Hall"]["Hire Options"][2].Commercial
After Looping Path of required key-value pair for all halls, not just one (the hall identifier is stored):
[0]["Hire Options"][2].Commercial
Looping allows me to check each hall for a specific key-value pair (kind of like map or forEach, but for an object).
After getting that out of the way back to the question.
How would I go about filtering which of the looped objects are displayed?
What I have Tried
(userInput is defined elsewhere - this happens on a btn click btw)
let results = Object.keys(halls);
for (key of results) {
let weekend = [halls[ `${key}` ][ 'Hire Options' ][4][ 'Weekend function' ]];
if(userInput == weekend) {
outputAll([halls[ `${key}` ]]);
}
}
That filters it fine. However, I run into an issue here. I want to filter by multiple queries, and naturally adding an AND into the if statement doesn't work. I also dont want to have 10 if statements (I have 10+ filters of various data types I need to sort by).
I have recently heard of ternary operators, but do not know enough about them to know if that is the correct thing to do? If so, how? Also had a brief loook at switches, but doesnt seem to look like what I want (correct me if I am wrong.)
Actual Question minus the babble/explanation
Is there a way for me to dynamically modify an if statements conditions? Such as adding or removing conditions of an if statement? Such as if the filter for 'a' is set to off, remove the AND condition for 'a' in the if statement? This would mean that the results would only filter with the active filters.
Any help, comments or 'why haven't you tried this' remark are greatly appreciated!
Thanks!
Just for extra reference, here is the code for retrieving each of the objects from the first object as it loops through them:
(Looping Code)
halls = data[ 'Halls' ];
let results = Object.keys(halls);
for (key of results) {
let arr = [halls[ `${key}` ]];
outputAll(arr);
}
You can use Array.filter on the keys array - you can structure the logic for a match how you like - just make it return true if a match is found and the element needs to be displayed.
let results = Object.keys(halls);
results.filter(key => {
if (userInput == halls[key]['Hire Options'][4]['Weekend function']) {
return true;
}
if (some other condition you want to match) {
return true;
}
return false;
}).forEach(key => outputAll([halls[key]]));
In my web application I receive a JSON string from the server which I keep in the greetings variable:
var greetings = '{"2":"hoi","3":"hi","1":"salam"}'
Please notice how the greetings start with the index 2 and the value hoi.
Now I want to parse the JSON and the result is the following:
JSON.parse(greetings) // {1: "salam", 2: "hoi", 3: "hi"}
The order has changed, it seems like JSON.parse orders the result by key.
Is there a way to keep the order of the original string intact?
{
"2":"hoi",
"3":"hi",
"1":"salam"
}
is not an array, its an object. Objects don't have any order.
If the order is important, you need to switch to an actual array.
You generally cannot rely on the order of indices in an object. Use an array of key/value pairs instead.
As you can see the keys are parsed to (numeric) indices, which is why they are ordered that way. You could hack around this by prefixing your keys and then stripping those later:
console.log(JSON.parse('{"i2":"hoi","i3":"hi","i1":"salam"}'))
I would like to substract json entries from the main JSON bulk data, based on an input, in JavaScript. Each entry in the main JSON data has it's own unique ID, but the filter should be based on the text identifier rather than the ID. I would like to retrieve for example all entries that contain the word burg (Burg, BURG, bUrg, etc.) or any other given variety. This should of course also work with other search terms. I do not possess the JavaScript skills to do this.
In the data given below this should return 3 results. Obviously, the result should be the exact same JSON format.
Example JSON:
{"type":"FeatureCollection","features":[{"id":1,"text":"Cape Town"},{"id":2,"text":"Kimberley"},{"id":3,"text":"Beaufort West"},{"id":4,"text":"Johannesburg Park"},{"id":5,"text":"Germiston"},{"id":6,"text":"Pietermaritzburg"},{"id":7,"text":"Durban"},{"id":8,"text":"Bellville"},{"id":9,"text":"Wellington"},{"id":10,"text":"Huguenot"},{"id":11,"text":"Worcester"},{"id":12,"text":"Matjiesfontein"},{"id":13,"text":"Laingsburg"},{"id":14,"text":"Prince Albert"},{"id":15,"text":"Hutchinson"},{"id":16,"text":"De Aar"},{"id":17,"text":"Warrenton"}]}
Do not use JavaScript for this. Use SQL and its LIKE operator instead.
But if you insist on using JavaScript for this…
Just like HTML, regular expressions cannot fully parse JSON because of serialization.
Filtering after JSON.parse is quite easy however; you can use the Array.prototype.filter() method:
var s = '{"type":"FeatureCollection","features":[{"id":1,"text":"Cape Town"},{"id":2,"text":"Kimberley"},{"id":3,"text":"Beaufort West"},{"id":4,"text":"Johannesburg Park"},{"id":5,"text":"Germiston"},{"id":6,"text":"Pietermaritzburg"},{"id":7,"text":"Durban"},{"id":8,"text":"Bellville"},{"id":9,"text":"Wellington"},{"id":10,"text":"Huguenot"},{"id":11,"text":"Worcester"},{"id":12,"text":"Matjiesfontein"},{"id":13,"text":"Laingsburg"},{"id":14,"text":"Prince Albert"},{"id":15,"text":"Hutchinson"},{"id":16,"text":"De Aar"},{"id":17,"text":"Warrenton"}]}';
var input = "burg";
var o = JSON.parse(s);
o.features = o.features.filter(e => RegExp(input, 'i').test(e.text));
console.log(JSON.stringify(o));
I have a multi-dimensional array like this:
1 2 3
4 5 6
Now I need to convert this array into a string like 1,2,3;4,5,6.
Can any one suggest how to do this, please?
simply use the join method on the array.
> [[1,2,3],[4,5,6]].join(';')
'1,2,3;4,5,6'
It's lucky that you simply don't have to consider how the apply the join method on the inner lists, because a list is joined by comma by default. when a list is coerced into a string, it by default uses commas to separate the items.
As it was already mentioned by qiao, join() is not recursive.
But if you handle the recursion yourself you should acquire the desired result, although in a rather inelegant way.
var array = [[1,2,3],[5,6,7]];
var result = [];
array.forEach(
function(el){
result.push(
el.join(",")
);
});
result.join(";");
If you need to serialize an array into a string and then deserialize it later to get an array from the string you might want to take a look at JSON:
http://www.openjs.com/scripts/data/json_encode.php
Try this:
array.toString();
See here for reference: http://www.w3schools.com/jsref/jsref_tostring_array.asp
See answer by qiao for a much nicer approach to multidimensional arrays like this.
I'm trying to stringify a multi-array variable into a JSON string in Javascript. The
//i'm using functions from http://www.json.org/json2.js
var info = new Array(max);
for (var i=0; i<max; i++) {
var coordinate = [25 , 32];
info[i] = coordinate;
}
var result = JSON.stringify(info);
But result doesn't look like a JSON string at all. What am I doing wrong here?
You, and many in this question, are confused about the JSON specification. The string you have is a valid JSON array.
From json.org
JSON is built on two structures:
A collection of name/value pairs. In various languages, this is
realized as an object, record,
struct, dictionary, hash table,
keyed list, or associative array.
An ordered list of values. In most languages, this is realized as
an array, vector, list, or
sequence.
Your example matches the second structure - the ordered list of values.
Also from json.org:
An array is an ordered collection of
values. An array begins with [ (left
bracket) and ends with ] (right
bracket). Values are separated by ,
(comma).
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.
Doesn't leave much to the imagination. You've got a valid JSON array there. Have fun with it. But just to be annoyingly thorough:
From the RFC
RFC 4627, Section 2
2) JSON Grammar
A JSON text is a sequence of
tokens. The set of tokens includes
six structural characters, strings,
numbers, and three literal names.
A JSON text is a serialized object
or array.
JSON-text = object / array
The result looks like this for me:
[[25,32],[25,32],[25,32],[25,32],[25,32],[25,32],[25,32],[25,32],[25,32],[25,32]]
Which is fine as far as I can see. It might look a bit weird, but that is mostly because JSON is used a lot for objects, which have a slightly different notation. You can eval the string and get the array structure back though, so it looks fine to me.