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I have node red successfully running and am feeding it from a couple of different PLC systems,
I have a payload like this.
{"d":779,"dt":3,"ts":"2018-04-05T19:54:12.930758Z","q":18}
The fields would break down to.
d=779 dt=3 ts=2018-04-05T19:54:12.930758Z q=18
I have been attempting to parse the string and break it down (even just one field "d").
I have been trying to write a function to parse the data using combinations of splice and split.
Does anyone have a simple solution to this? Am I even using the correct node process?
I know this is completely not working but it was an attempt the read the first field. It is not padded and therefore needs to start where the colon is and end with the comma.
var str = msg.payload;
var th = str.slice(5,-1);
th = th.split(",");
msg.payload[0] = parseFloat(th[0]);
return [ msg.payload[0]];
Have a source MQTT Buffer of:
[123,34,100,34,58,51,48,54,56,44,34,100,116,34,58,50,44,34,116,115,34,58,34,50,48,49,56,45,48,52,45,49,50,84,48,56,58,53,48,58,49,56,46,49,54,50,48,48,48,90,34,44,34,113,34,58,49,57,50,125,0]
The Zero at the end is obviously the offending value:
I am attempting to remove it with function
var data = msg.payload;
console.log("payload data: length = " + data.length);
data = data.trim();
console.log("trimmed data: length = " + data.length);
msg.payload = JSON.parse(data);
return msg;
Now am getting TypeError: data.trim is not a function
Flow looks like:
enter image description here
Now getting
Thanks,
Kevin
By default most nodes will be outputing a JSON object already so there will be no need to parse it as a string just access the objects values directly e.g.
var d = msg.payload.d;
If the nodes are output String representations of JSON then you should use the built in JSON node to convert the string in msg.payload to a JSON object before accessing the values.
Also you need to return a whole JSON object from a function node, not just a string (or an array of strings)
So if you just want to the pass the d value on it should be:
var d = msg.payload.d;
msg.payload = d;
return d;
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'm using Socket.IO to move data to the browser. The data sent is a stream of JSON objects, and when it arrives at the browser, it becomes one large string of JSON. The problem is, this JSON can't be parsed by JSON.parse() because it's not "real" JSON.
The data structure can be arbitrary so a RegEx might not do the trick. And this current setup is only temporary. Eventually this stream of JSON will be pre-processed server-side so a stream will not need to be sent to the browser, so I'd like to keep the AJAX/Socket.IO setup I have right now instead of switching over to a JSON stream parser like OboeJS.
What can I do to parse this string of concatenated JSON?
For clarity, the JSON will look like this:
{"a":"A"}{"b":"B"}{"c":"C"}
And I'm trying to parse it in such a way that I can access them like:
console.log(Object.a) //A
console.log(Object.b) //B
console.log(Object.c) //C
In your particular case, you could use Array.prototype.reduce to merge all JSON objects into one:
var unstructuredJson = '{"a":"A"}{"b":"B"}{"c":"C"}';
var jsonArray = "[" + unstructuredJson.split("}{").join("},{") + "]";
var objectArray = JSON.parse(jsonArray);
var result = objectArray.reduce(function(result, item) {
Object.keys(item).forEach(function(propertyName) {
result[propertyName] = item[propertyName];
});
return result;
}, {});
document.body.textContent = JSON.stringify(result);
OP said in some comment:
[...] Each JSON might have nested data like {{}{}}{}{}{}
Then, above approach is broken on this case.
My two cents is that you should put some separator character when you stream these JSON objects and life will be easier: you'll be able to split parent objects easily and you'll just need to change split("}{") with the whole separator.
I suggest you that you use some character that will never happen as part of any property value. You can find a control character on this Wikipedia article: Control character
If each substring is valid JSON but the concatenated part isn't, you can turn the string into a valid array literal and use JSON.parse, then you can process each object using Array methods, e.g. forEach:
var s = '{"a":"A"}{"b":"B"}{"c":"C"}';
var obj = JSON.parse('[' + s.replace(/}{/g,'},{') + ']').forEach(function (obj) {
document.write(JSON.stringify(obj) + '<br>');
});
Or if you want it as a single object:
var s = '{"a":"A"}{"b":"B"}{"c":"C"}';
var obj = JSON.parse(s.replace(/}{/g,','));
document.write(JSON.stringify(obj));
You can use JsonParser to parse concatenated json objects:
ObjectMapper mapper = new ObjectMapper();
JsonFactory factory = new JsonFactory(mapper);
JsonParser parser = factory.createParser(YourJsonString);
List<YourObject> YourObjectList = new ArrayList<>();
Iterator<YourObject> iterator = parser.readValuesAs(YourObject.class);
while(iterator.hasNext()) {
YourObject yourObject = iterator.next();
loginSignalsList.add(yourObject);
}
Split the large string {a:'A'}{b:'B'}{c:'C'} and parse them individually
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);
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.