When we can read a property directly from string:
var data = {"id":1,"name":"abc","address":{"streetName":"cde","streetId":2}};
console.log(data.address.streetName); // cde
Why do people use JSON.parse:
var obj = JSON.parse(data);
console.log(obj.address.streetName); // cde
It is not a string, but Javascript object. String is given below
var data = '{"id":1,"name":"abc","address":{"streetName":"cde","streetId":2}}';
to make it object we use JSON.parse
var obj = JSON.parse(data);
console.log(obj.address.streetName); // cde
In your first example, data is an object, but in your second example, data is a JSON string.
That's a major difference. You could call eval(data) to parse a JSON string, but that's very unsafe.
JSON.parse() expects a string. More specifically, a string with a JSON-encoded piece of data.
If it's applied to an object then it's an error, the source of which is probably the common confusion that seems to exist between JavaScript objects and the JSON format.
Related
how can i take this json data (either from website or pasted into local file) and read it into a javascript object?
Here is the json data: https://jsonblob.com/b914b62a-e276-11e7-8a9c-f99a86745e2b
You can convert an JSON file to an object by using JSON.parse
let convertedObject = JSON.parse(text)
There are not many differences between a JSON string and a Javascript Object. In fact Everything is an object in javascript, from functions to arrays...well coming back to your question you can get the value stored in a JSON string by parsing the JSON string by using JSON.parse() function and then call it as you generally do with JS objects. for Example: -
var jsonString = JSON.stringify({key: "val"}); // here i am converting a regular object to JSON string
var jsonToObj = JSON.parse(jsonString);
console.log(jsonToObj.key);
I am trying to access the t part of the "data": object below. I am doing this by doing console.log(message.data.f) however this returns undefined. I do not understand why I cannot access it in this way. See object below:
"data":"{\"e\":\"53845\",\"f\":\"SCORE\",\"pf\":[{\"p\":\"HOME\",\"v\":\"0\"},{\"p\":\"AWAY\",\"v\":\"0\"}],\"^t\":\"f\",\"i\":\"357575\",\"z\":1492771602631}",
Note I have marked the part of the object I wish to access with a ^
Your data property is a JSON string and probably all the object is a JSON string.
You need to parse the string as JSON
var obj = JSON.parse(myObj.data);
and then you can access:
console.log(obj.f);
If your first object, the one containing data, is not already a JSON too and its name is for example myFirstObject you need to do just this:
var jsonObj = JSON.parse(myFirstObject);
console.log(jsonObj.f);
Your message is nothing but string. Parse it first to a corresponding object to access its variables.
var parsed = JSON.parse(message);
console.log(message.data.t);
I have a string variable containg JSON data as below.
var jsonstring = [{"latitude":"51.5263","longitude":"-0.120285","altitude":"","device":"123","rating":"5","region":"Europe","customer":"","time":"1-2 Weeks","error":"Error 1","application":"Phone","age":"< 1 Year"},
{"latitude":"27.58","longitude":"23.43","altitude":"","device":"Asc 140","rating":"4","region":"Africa","customer":"","time":"< 1 Week","error":"Error 1","application":"PCB","age":"1-3 Years"},
{"latitude":"39.55","longitude":"116.25","altitude":"","device":"CVB","rating":"4","region":"China","customer":"","time":"1-2 Weeks","error":"Error 2","application":"Sorting","age":"3-5 Years"}]
I want to get this string and convert it to an array of objects (which would be a $scope.variable) so that i can be able to access each object individually.
I tried to use the JSON.parse() but it gets the entire string into one object instead of multiple objects.
Kindly help me with this.
You've to parse the entire string with JSON.parse.
Each object in the array can then be reached like any other array, e.g. myArray[index], myArray.map() / myArray.forEach() etc
[{"latitude":"51.5263","longitude":"-0.120285","altitude":"","device":"123","rating":"5","region":"Europe","customer":"","time":"1-2 Weeks","error":"Error 1","application":"Phone","age":"< 1 Year"},
{"latitude":"27.58","longitude":"23.43","altitude":"","device":"Asc 140","rating":"4","region":"Africa","customer":"","time":"< 1 Week","error":"Error 1","application":"PCB","age":"1-3 Years"},
{"latitude":"39.55","longitude":"116.25","altitude":"","device":"CVB","rating":"4","region":"China","customer":"","time":"1-2 Weeks","error":"Error 2","application":"Sorting","age":"3-5 Years"}]
This is an array object.It's not a string object.
You can try again like this:
var jsonString = "[]";
var json = JSON.parse(jsonString);
var jsonstring = '[{"latitude":"51.5263","longitude":"-0.120285","altitude":"","device":"123","rating":"5","region":"Europe","customer":"","time":"1-2 Weeks","error":"Error 1","application":"Phone","age":"< 1 Year"}, {"latitude":"27.58","longitude":"23.43","altitude":"","device":"Asc 140","rating":"4","region":"Africa","customer":"","time":"< 1 Week","error":"Error 1","application":"PCB","age":"1-3 Years"}, {"latitude":"39.55","longitude":"116.25","altitude":"","device":"CVB","rating":"4","region":"China","customer":"","time":"1-2 Weeks","error":"Error 2","application":"Sorting","age":"3-5 Years"}]';
$scope.variable = JSON.parse(jsonstring);
The JSON.parse() method parses a string as JSON.
Code in your question, shows that you are trying to parse a JS object and not a string.
In the following example, you get an error if you try to parse a JS object.
var jsonstring = [{},{}];
JSON.parse(jsonstring); // ERROR Uncaught SyntaxError: Unexpected token o
The following works instead (please note jsonstring is a string and not an object here):
var jsonstring = '[{},{}]';
JSON.parse(jsonstring); // OK
I have not worked too much on javascript. And, I need to parse a JSON string. So, I want to know what exactly JSON.parse does. For example :
If I assign a json string to a variable like this,
var ab = {"name":"abcd", "details":{"address":"pqrst", "Phone":1234567890}};
Now when I print 'ab', I get an object.
Similarly when I do this :
var pq = '{"name":"abcd", "details":{"address":"pqrst", "Phone":1234567890}}';
var rs = JSON.parse(pq);
The 'rs' is the same object as 'ab'. So what is the difference in two approaches and what does JSON.parse did differently ?
This might be a silly question. But it would be helpful if anybody can explain this.
Thanks.
A Javascript object is a data type in Javascript - it's have property and value pair as you define in your first example.
var ab = {"name":"abcd", "details":{"address":"pqrst", "Phone":1234567890}};
Now What is Json : A JSON string is a data interchange format - it is nothing more than a bunch of characters formatted a particular way (in order for different programs to communicate with each other)
var pq = '{"name":"abcd", "details":{"address":"pqrst", "Phone":1234567890}}';
so it's is a String With json Format.
and at last JSON.parse() Returns the Object corresponding to the given JSON text.
Here is my explanation with a jsfiddle.
//this is already a valid javascript object
//no need for you to use JSON.parse()
var obj1 = {"name":"abcd", "details":"1234"};
console.log(obj1);
//assume you want to pass a json* in your code with an ajax request
//you will receive a string formatted like a javascript object
var str1 = '{"name":"abcd", "details":"1234"}';
console.log(str1);
//in your code you probably want to treat it as an object
//so in order to do so you will use JSON.parse(), which will
//parse the string into a javascript object
var obj2 = JSON.parse(str1);
console.log(obj2);
JSON, or JavaScript Object Notation, is a minimal, readable format for structuring data. It is used primarily to transmit data between a server and web application, as an alternative to XML.
Your 'ab' variable isn't a string, it is a proper javascript object, since you used the {} around it. If you encased the whole thing in "" then it would be a string and would print out as a single line.
Data Type!! That is the answer.
In this case, ab is an object while pq is a string (vaguely speaking). Print is just an operation that displays 'anything' as a string. However, you have to look at the two differently.
String itself is an object which has properties and methods associated with it. In this case, pq is like an object which has a value: {"name":"abcd", "details":{"address":"pqrst", "Phone":1234567890}} and for example, it has a property called length whose value is 66.
But ab is an object and you can look at name and details as its properties.
What JSON.parse() did differently was that, it parsed (converted) that string into an object. Not all strings can be parsed into objects. Try passing {"name":"abc" and JSON.parse will throw an exception.
Before parsing, pq did not have any property name. If you did something like pq.name, it'll return you undefined. But when you parsed it using JSON.parse() then rs.name will return the string "abcd". But rs will not have the property length anymore because it is not a string. If you tried rs.length then you'll get a value undefined.
I have an array that is printed in JSON
[{"Name":"John Ranniel","Age":"19","City":"Manila"},{"Contact":"09197875656","Relation":"Sister"}]
For some reason, I divided the JSON into two parts.
In javascript I used JSON.parse() to decode the JSON above.
for example:
var arr = JSON.parse(response); //The response variable contains the above JSON
alert(arr[0].Name) //Still it outputs John Ranniel, but If i change the content of the alert box on the second part of the JSON,
alert(arr[1].Contact) // It has no output, I don't know if there is a problem with the index of the array.
Make sure your JSON is a string type:
'[{"Name":"John Ranniel","Age":"19","City":"Manila"},{"Emergency Contact":"09197875656","Relation":"Sister"}]'
and then, you can use,
var arr = JSON.parse(response); //The response variable contains the above JSON
console.log(arr[0].Name);
console.log(arr[1]['Emergency Contact']); // There is no 'Contact' property iun your object, and you should use this when there's a space in the name of the property.
See:
var response = '[{"Name":"John Ranniel","Age":"19","City":"Manila"},{"Emergency Contact":"09197875656","Relation":"Sister"}]';
var arr = JSON.parse(response);
console.log(arr[0].Name);
console.log(arr[1]['Emergency Contact']); // There is no 'Contact' property iun your object, and you should use this when there's a space in the name of the property.
You are trying to parse something which is already a JavaScript object, and does not need to be parsed. You need to parse JSON strings. This is not a JSON string. It's a JavaScript object.
Consider the following:
JSON.parse([1,2])
This will coerce the array [1,2] into the string "1,2". JSON.parse will then choke on the ,, since it doesn't belong there in a valid JSON string.
In your case the object will be coerced to the string
"[object Object],[object Object]"
JSON.parse will accept the leading [ as the beginning of the array, then throw on the following character, the o, since it does not belong there in a proper JSON string.
But you say that the JSON.parse worked and resulted in arr. In other words, the parameter you fed to JSON.parse apparently was a string, and was parsed correctly. In that case, the alerts will work fine.
Your JSON structure is array, must be parse to JSON,use JSON.stringify parse this to JSON:
var json = [{"Name":"John Ranniel","Age":"19","City":"Manila"},{"Contact":"09197875656","Relation":"Sister"}];
var str = JSON.stringify(json);
console.log(json);
var arr = JSON.parse(str);
alert(arr[0].Name) //Still it outputs John Ranniel, but If i change the content of the alert box on the second part of the JSON,
alert(arr[1].Contact) // It has no output, I don't know if there is a problem with the index of the array.
Demo: Link
This JSON is array, you can use directly:
var json = [{"Name":"John Ranniel","Age":"19","City":"Manila"},{"Contact":"09197875656","Relation":"Sister"}];
alert(json[0].Name);
alert(json[1].Contact);