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Best way to concatenate multiple strings?

I have a project, where user can put in drop-down values that can be selected. One can select multiple values at a time. So, we have to store the selection and get it on edit mode.
First thought
Let's store them as comma separated in DB.
f.e.
If suggestions are A , B , C and user selects A and B, I was going to store A,B in DB and while getting back the value split it with comma.
Problem arises when user has genuine "comma" in the field, for an instance first,option & second,option. At that time joining with comma won't work.
Second thought
I can think of another option to store it in a stringified array format and parse it while getting back.
For the above instance, it would store the data as ["first,option","second,option"]. It seems to be a good (and only) option for me.
Even though I have a bit of hesitation doing so (which lead me questioning here!) because my users can access the api/DB value directly and for them it doesn't look good.
So, Is there any other way to address this issue to benefit both parties, developers and users? Thanks in advance!!

I'd suggest using a standardized format such as JSON, XML etc.
Serialize and parse and with a widely used library so all escaping of reserved / special characters is done for you. Rolling your own here will cause you problems!
Better yet, use different fields for each suggestion, this is a better design in general. As long as the number of potential fields is finite this will work, e.g. 1-10 suggestions.
If you're going down the JSON route, we can do this in JavaScript like this:
let suggestions = ['Choice A, commas are not, a problem, though punctuation is.', 'Choice B', 'Choice C'];
let json = JSON.stringify(suggestions);
// Save to DB
saveToDB(json);
let jsonFromDB = loadFromDB();
let deserializedSuggestions = JSON.parse(jsonFromDB);
console.log(deserializedSuggestions);

we use semicolon (;) for this exact use case in our current project.
So, as per your question, they will be stored in the DB as option1;option2;option3
and when we get it back from the DB we can use the split() method on it to convert it into an array of substrings.
var str = "option1;option2;option3";
var res = str.split(";");
console.log(res);
which would result in (3) ["option1", "option2", "option3"] in the console.
hope this helps.

Convert JSON with objects and arrays to String

I have a JSON object which looks like this:
{
files: ['test.mp4'],
name: ['testFile'],
hints: ['%YES%_%MAYBE%_%NO%']
}
And I need to convert it to a String so the output looks like this:
[{files=test, name=testFile, hints= %YES%_%MAYBE%_%NO%}]
Is this possible to achieve in Node JS? Thanks
I tried the following:
var x = {
files: ['test.mp4'],
name: ['testFile'],
hints: ['%YES%_%MAYBE%_%NO%']
}
console.log(JSON.stringify(x));
But the output looks like this:
{"files":["test.mp4"],"name":["testFile"],"hints":["%YES%_%MAYBE%_%NO%"]}
Still with the square brackets. I may not 100% know the keys and values in the object above.

Try
JSON.stringify(obj)
then you get a string with quotes etc.

JavaScript has JSON.stringify() method which can convert an object into string:
var x = {
files: ['test.mp4'],
name: ['testFile'],
hints: ['%YES%_%MAYBE%_%NO%']
}
console.log(JSON.stringify(x));
// result: '{"files":["test.mp4"],"name":["testFile"],"hints":["%YES%_%MAYBE%_%NO%"]}'
This will result in a string which can be transformed back to JS object with JSON.parse() method. If you still want to remove all brackets and quotes, you can simply use JavaScript's replace() method (replacing characters [, ], and " with empty string), but this will replace those characters in all your values (if any) and will result in (sort of) non-reusable string.

TL;DR Don't do this unless you absolutely have to (ie. you're dealing with a messed up API written by someone else that must have the data in this format)
If you want exactly the format listed in your question, then you're going to have to write your own stringify function that recursively walks through the object you pass to it and applies whatever rules you want to use. You will have to consider all the possible permutations of your object and spell out those rules.
For example, you've converted arrays with single elements in the initial object into strings - what happens if there is more than one element in the array? Should it be delimited by a comma or some other character? Should we just throw away elements after the first?
And once you've written the stringify function, you'll also have to write the corresponding parse function to reverse it. And it should be mentioned that in your example, you're throwing away information (eg. the file extension on the .mp4 file) - how are you going to handle that?
A much, much better way to approach this would be to do what other people have suggested here: use JSON.stringify and rewrite your code to use standard JSON objects. Why? Because the format is well documented and well understood and because the functions to convert are well tested. You will save yourself a whole lot of time and pain if you don't try to reinvent the wheel here.

JSON.parse & JSON.stringify handling long integers as strings

I have the problem, that I need to parse long integers in my API. Since I don't do anything arithmetically, it is the easiest to handle them as Strings. I tried Bignumber.js, but it starts complaining if numbers are longer than 15 characters. Unfortunately I have to handle them as well.
Since I don't do anything arithmetically with it and actually even store those numbers as String I would like a JSON Parser that parses too big numbers as Strings and is capable of also treat them as numbers in JSON.stringify.
I tried the stringify with a replacer function, but I could not get rid of the quotes around my number.
I also did not find a library, that just takes care of this issue.
Edit / Clarification
I want my big number to be a String in javascript, but a number in JSON (after JSON.stringify)
e.g. Object in Javascript
var myObj = {
id: "89074987798719283473" // <-- String within javascript
}
var objString = JSON.stringify(myObj)
Now my objString should be
{id: 89074987798719283473}
And NOT
{id: "89074987798719283473"}

If you absolutely must do this and really can't find a better place to handle this, then remember that JSON is just a string, and all the tools for string manipulation can be brought to bear on this problem. So you could do something like:
var myObj = {
id: "89074987798719283473" // <-- String within javascript
}
var json = JSON.stringify(myObj); // this is {"id":"89074987798719283473"}
var numberJson = json.replace(/"id":"(\d+)"/,'"id":$1'); // this is now {"id":89074987798719283473}
console.log(numberJson);
Of course this is hacky and error prone as you have to be very careful about what you are matching (you might have other properties called id nested in your json that you don't want manipulated). If you wanted to make it a little more robust, you could append something the end of your id before you stringify to make it easier to find and replace it in the string.

How to generate a JSON object dynamically with duplicate keys?

I know this will sound impossible but my boss told me I MUST send a JSON over an AJAX post call with jQuery that MUST HAVE DUPLICATE KEYS. the problem is that if I write something like this:
$.post("someurl", {
"key1" : "value1",
"key2" : "value2",
"key2" : "value3",
"key2" : "value4",
"key3" : "value5"
});
, jQuery will send the request as
someurl?key1=value1&key2=value4&key3=value5
all this because Javascript overwrites properties that have the same name. The JSON object is generated dynamically and I am NOT ALLOWED to use arrays in it. Can someone tell me how could I generate the JSON object dinamicaly and with duplicate keys?
I would realy appreciate any help from you!

From what I can see, {"a": "b", "a": "c"} actually is valid JSON according to RFC 4627.
An object structure is represented as a pair of curly brackets
surrounding zero or more name/value pairs (or members). A name is a
string. A single colon comes after each name, separating the name
from the value. A single comma separates a value from a following
name. The names within an object SHOULD be unique.
...where SHOULD means:
3. SHOULD. This word, or the adjective "RECOMMENDED", mean that there
may exist valid reasons in particular circumstances to ignore a
particular item, but the full implications must be understood and
carefully weighed before choosing a different course.
So yeah, basically you can do that, it is legal, but it's also a bad idea. Different JSON decoders will probably handle this situation differently and/or in undesiderable ways. Look at what the spec requires of parsers:
A JSON parser transforms a JSON text into another representation. A
JSON parser MUST accept all texts that conform to the JSON grammar.
A JSON parser MAY accept non-JSON forms or extensions.
An implementation may set limits on the size of texts that it
accepts. An implementation may set limits on the maximum depth of
nesting. An implementation may set limits on the range of numbers.
An implementation may set limits on the length and character contents
of strings.
...but an implementation doesn't have to handle situations like this sanely. For example:
# Python 2.7
>>> import json
>>> json.JSONDecoder().decode('{"a": "b", "a": "c"}')
`{u'a': u'c'}`
# Chrome 32
> JSON.parse('{"a": "b", "a": "c"}')
Object {a: "c"}
...and other implementations may legally give you (in Python notation):
{"a": "b"}
[("a", "b"), ("a", "c")]
[("a", ["b", "c"])]
[]
42
"your JSON is bad and you should feel bad"
...or just good old nasal daemons. Literally the only illegal thing for a JSON parser to do here is raise an exception.
The last thing you want to do in your production code is to rely on weird side cases. So the last thing you want to do is exercise your right to form nominally legal but practically useless JSON. If you want to do that, you'll have to do it by hand - build your own abstract syntax trees, your own parsers, your own generators, generators for anybody who might want to consume your data...

A Javascript object with duplicate keys is not a Javascript object. In fact, it is no more than a figment of your imagination. It is totally impossible.
The only way to do this is with an array:
{
"key1" : "value1",
"key2" : ["value2", "value3", "value4"],
"key3" : "value5"
}
jQuery will convert this into key1=value1&key2%5B%5D=value2&key2%5B%5D=value3&key2%5B%5D=value4&key3=value5
This is genuinely the only way to do this.* Is there a reason why your code cannot generate valid JSON?
* Except for writing your own parser that handles invalid JSON. But that would be breathtakingly stupid.

I would do it only if the JSON parser on the other side accepts it properly, without dropping anything. If you can show it dropping stuff, then you can look for another solution (like using an array, or generating the JSON by hand, or using a URL properly. You need better test cases first for your server.

If you can't change the source at the source, then change the source into something you can at least work with...
Parse the JSON into an Array of key value pairs (not into an object of key/value pairs).
You could do this easily if you have access to the JSON string, simply replace all "," with "},{" and wrap the result in "[" and "]".
You now have a valid JSON array of key/value pairs that is javascript legal.

Variable in JSON

I don't have much experience with JSON, I want to know if something like this is possible.
{
"variable": "A really long value that will take up a lot of space if repeated",
"array": [variable, variable, variable]
}
Obviously that isn't valid, but I want to know if there is a way to do this. I tried using "variable" but of course that just sets the array item to the string "variable". The reason I want to do this is I need to repeat long values in a multidimensional array, which takes up a lot of space.
Thanks.

If you are willing to do some post-processing on the JSON after parsing it, then you can use a token value in your array, and replace the token after parsing with the variable. Example:
{
"variable": "A really long value",
"array": ["variable", "variable", "variable"]
}
Then, in your code that parses:
var obj = JSON.parse(str);
for (var i=0; i<obj.array.length; i++)
{
obj.array[i] = obj[obj.array[i]];
}

Are you worried about space in the output, or in the object created from the JSON? In the latter case, it's likely that the string values will be coalesced when the parsing happens.
If you're concerned about the size of the JSON, then you'll probably either want to change to another format, or de-duplicate the strings in the JSON.
You could add an object to your JSON data that maps ID numbers to strings, then use the IDs to represent te strings.

There is no way to do this in pure JSON (full spec here).
If you wanted to do something like that you might want to look into templating tools such as Handlebars

you will get your answer here jason tutorial for beginners
example:
var data={
"firstName":"Ray",
"lastName":"Villalobos",
"joined":2012
};