By JSON text, I mean the return value of JSON.stringify. I know how to do this with JSON object, but I couldn't figure out how to do this with JSON text (add new attribute/element, say "sn":"1" to JSON text, but its structure is kept and I don't need to stringify it again), can anyone help me?
Thanks!
I don't know why you'd want to do this - why not just add the property before you stringify it?
But if you must, given a string that contains JSON:
var myJSON = '{"prop1":"val1","prop2":"val2"}';
You can easily add a property to the beginning by doing this:
myJSON = '{' + '"sn":"1",' + myJSON.substr(1);
Or add it to the end:
myJSON = myJSON.replace(/}$/, ',"sn":"1"' + '}');
Or use whatever other combination of String manipulation functions takes your fancy...
If you want to add the new property in a specific place within the string, say inside a nested object or array or something, well, again some kind of regex or combination of .indexOf() and .substr() or something could do it, but really I think it's nuts to approach it this way.
Obviously the above code can be wrapped up in a function, and '"sn":"1"' can be replaced with a parameter or variable name or whatever - but why?
Note also that I've assumed above that there will be at least one existing property and inserted a comma accordingly- up to you to make that smarter if you want to allow for empty objects.
P.S. There aren't "JSON strings" and "JSON objects": all JSON is a string. In JavaScript one way of creating objects is with the object literal syntax that inspired JSON, but there's no such thing as a JSON object.
It makes no sense to do it the way you're suggesting... just turn it back into an Object, add your field and stringify it again! Or am I missing something?
You're going to have to parse it somehow. The most straightforward way is probably un-stringifying it to object/array/literal data. But if you don't want to do that, you could either use regular expressions, or methods of the String object like substr to manipulate the string directly.
Related
I have two variables with JSON files. The first is a list of keys looks like this:
keylist = ["key1","key2","key3"]
The second one is generated from a database and looks like this:
data = {
"key1"{
#further data
},
"key2"{
#further data
},
"key3"{
#further data
}
}
Now I want to access the second element of the database with the key from the keylist
data.keylist[1];
Which doesn't work because the return of keylist[1] is a String? I did some research and the use of the window function was proposed. So I tried this:
window["data." + keylist[1]]();
Which leads to a "is not a function" error. What can I do to solve this problem?
As simple as that:
const mydata = data[ keylist[1] ];
Also, your code is correct from the point of syntax, but it tells completely different than you expect it to tell.
data.keylist[1];
tells JS that you expect to have an object called data which has a property called keylist and which is (most likely) type of array, and you want to get the second element of this array.
PS: And one more point here. Your question title is not completely correct because of the difference between Arrays and Object in JS.
There is no "string keys" for arrays in JS, so you cannot "access array with a string key". Well, truly speaking there are, but not for items of array. Array items only have numeric index, which you can use to access it. Objects, in contrast to arrays, may have named properties. So when you see something like that: data = myVar['data'], you can tell that you're dealing with an object, while data = someVar[0] can be both, an Array (most likely) or also an Object with key named '0'.
I don't think the issue you're having with your first example is because it returns a key. I believe the issue is because data doesn't have a property called keylist. Instead of that, try it as
data[keylist[1]]
and see if that works for you. The reason this one should work is that, in this situation, Javascript will evaluate the string return of keylist[1] and then use it as a string index for the data variable. Let me know if this works out for you :D
You can try using using something like this.
data[keylist[1]]
I am trying to return the value under the key 'str' in an Object but I am having trouble accessing the value.
This is what is returned in the console:
Currently I am using a map function to go over the array and just return the _str value like so:
let idx = currentArray.map(function(x) {
return x._id._str;
});
However it is still returning the value as an object. How can I get just the value of the _str key?
Here is the full array without specifying the id field. This is what is returned if you jsut return 'x' in the map function.
You've clarified that the screenshot is of x._id. So to access _str, you'd use x._id[0]._str: The _str property is in the object referenced by the 0 property (the first entry in the array x._id refers to).
Note that in general, _-prefixed properties are meant not to be accessed by code outside the code responsible for the objects in question. You don't seem to be responsible for them, so accessing those properties is likely to make your code rely on undocumented properties that may change in the next "dot" release of whatever lib you're using. It's just convention, but it's a very common convention.
If you right click on the property, most browser consoles offer the ability to copy property path.
Based on this SO post and the docs, it appears that you can probably use x._id.str.
If I understand correctly, you are receiving the str value but it is an object instead of the string literal. In other words, you are getting _str: "598..." instead of "598....". A possible solution would be to use the mongo javascript function to convert the str value to a string.
In your case, I think something like return x._id.str; may work as _id is a MongoID.ObjectID.
I've also linked the documentation below for reference.
https://docs.mongodb.com/manual/reference/method/ObjectId/
Here's a relevant SO answer as well: Convert ObjectID (Mongodb) to String in JavaScript
I think you should write x[_id]._str because _id is one of the array objects.
I have created JSON by using the json_encode PHP function. The key of one of the items of the array contains a forward slash and when the JSON is parsed, the object looks like this when output in Chrome's console.
Object
contact/allow_anonymous: "0"
menulayout: "horizontal"
pages/max_pages: "10"
primarycolour: "329e95"
websitelogo: "text"
My problem is that I can't seem to be able to access the value of the properties that have a forward slash in them.
Any ideas? Since javascript allowed me to create the object I would assume there is a way to retrieve the values.
Just use myObject["key"] instead of myObject.key:
alert(myObject["contact/allow_anonymous"]);
Just replace the forward slash with ~1.
Instead of contact/allow_anonymous use contact~1allow_anonymous
Hello i have an url in my jsp and i want to pass an array of string in this url to recover in my ActionForm
If you are dealing with something simple like a list of numeric ids, i would just run through the check boxes, create a comma separated list, and assign it to a query string parameter. On the other side i would split the string.
If the values are more complex you have to consider escape characters. Also if you are dealing with a long list, the url is not the best way to pass this data.
You can use 'standard' html way of passing arrays of data: http://mywebsite/mypage?myarray=value1&myarray=value2&myarray=value3. Then you can fetch all values of parameter myarray from request object (if framework doesn't provide more elegant ways of handling arrays).
But seeing your comment, I would recommend to leave JavaScript and just declare a form for it.
If you need a link (not button), you can always submit form from it. Something like ...
Try Json encode
http://code.google.com/p/json-simple/
Check this
I'm trying to replicate a "feature" of PHP (And in most languages) in Javascript.
Here it is in PHP:
$objectName = 'ObjectA';
$someObject->$objectName->someMethod();
Basically using a string variable to reference an object variable.
So in Javascript, I was hoping to do something like:
var objectName = "ObjectA";
someObject.[objectName].someMethod();
Anyone know how to do this? Or if its even possible?
You almost have it, just remove the first ., like this:
var objectName = "ObjectA";
someObject[objectName].someMethod();
If you want to search for more info around this, it's called bracket notation.