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My node app receives a series of strings in the format "a=x b=y c=z" (i.e. a string containing several space-separated key=value pairs).

What is the neatest way of converting such a string into a JSON object of the form {a: x, b: y, c: z}?

I'm betting that there's a one-line solution, but haven't managed to find it yet.

Thanks.

My node app receives a series of strings in the format "a=x b=y c=z" (i.e. a string containing several space-separated key=value pairs).

What is the neatest way of converting such a string into a JSON object of the form {a: x, b: y, c: z}?

I'm betting that there's a one-line solution, but haven't managed to find it yet.

Thanks.

• javascript
• json

Share Improve this question Follow asked Aug 20, 2015 at 19:39 drmrbrewerdrmrbrewer 13k2323 gold badges9797 silver badges211211 bronze badges 2

• What kind of data is in the values? Strings? Numbers? – Andreas Hagen Commented Aug 20, 2015 at 19:44
• 1 You say that you want a "JSON object" as result, but there is no such thing. JSON is a text format for representing data. Do you want the result to be JSON or an object? – Guffa Commented Aug 20, 2015 at 19:49

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8 Answers 8

Sorted by: Reset to default 10

One way would be to replace the with a , and an = with a ::

var jsonStr = '{' + str.replace(/ /g, ', ').replace(/=/g, ': ') + '}';

Or if you need quotes around the keys and values:

var jsonStr2 = '{"' + str.replace(/ /g, '", "').replace(/=/g, '": "') + '"}';

---

JSON.parse() it if you need.

Sample output:

str:      a=x b=y c=z
jsonStr:  {a: x, b: y, c: z}
jsonStr2: {"a": "x", "b": "y", "c": "z"}

Building on John Bupit's excellent answer, I have made a couple of further enhancements to end up with the following (the string being parsed being in message):

var json = JSON.parse(('{"' + message.replace(/^\s+|\s+$/g,'').replace(/=(?=\s|$)/g, '="" ').replace(/\s+(?=([^"]*"[^"]*")*[^"]*$)/g, '", "').replace(/=/g, '": "') + '"}').replace(/""/g, '"'));

Basically the scheme is as follows:

1. First replace(): trim off any leading or trailing whitespace -- equivalent to trim()
2. Second replace(): add double quotes (empty string) for any value that is completely missing (e.g. key1= key2=val goes to key1="" key2=val).
3. Third replace(): replace each space (which acts as a delimiter) with ", ", but not where the space is within double quotes (i.e. part of a string value).
4. Fourth replace(): replace each = with ": "
5. Wrap the entire string up as follows: {"..."}
6. Finally, replace any double quotes "" created by the above steps (because the value string was already wrapped in quotes in message) with single quotes "
7. Even more finally, run JSON.parse() over the result.

The above scheme should cope with missing values, with some values being quoted and some unquoted, and with spaces within value strings, e.g. something like a= b="x" c="y y" d=z.

Assuming that you don't get nested objects in that format :

var sample = 'a=x b=y c=z';
var newobj = {};
sample.split(' ').forEach(function (value) {
    var keypair = value.split('=');
    newobj[keypair[0]] = keypair[1];
});
console.dir(newobj);

What this does is split on every white-space and push to an array, and the array is looped and each item in array is split again to get each key-value pair which is assigned to the newobj.

Here's a simple function that will do the trick

function stringToObj (string) {
  var obj = {}; 
  var stringArray = string.split(' '); 
  for(var i = 0; i < stringArray.length; i++){ 
    var kvp = stringArray[i].split('=');
    if(kvp[1]){
     obj[kvp[0]] = kvp[1] 
    }
  }
  return obj;
}

I would use an approach leveraging URLSearchParams and Object.fromEntries() like so:

const input = "a=x b=y c=z";

const queryString = input.replaceAll(" ", "&");
const query = new URLSearchParams(queryString);
const output = Object.fromEntries(query);

console.log(output);

Breakdown:

The URLSearchParams constructor takes a string of key-value pairs joined by "&" as it's argument, and parses it into a URLSearchParams object instance. So to use this, the space separators in the original input need to be replaced with a "&" character.

The URLSearchParams instance we have after parsing is an iterable, so we can transform it into a plain Object with Object.fromEntries().

It's not too bad as a one-liner either:

const input = "a=x b=y c=z";

const output = Object.fromEntries(new URLSearchParams(input.replaceAll(" ", "&")));

newstr = ""
for kvp in @value.split(" ")
  newstr += kvp.replace(/=/,'":"').replace(/^/, '"').replace(/$/, '"').replace(/\"\"/,'" "')

newstr = newstr.replace(/\"\"/g, '","')
jsn = JSON.parse('{' + newstr + '}')

I created a simple online tool for similar need: https://superal.github.io/online-tools/

Use cases:
To transfer key:value pairs copied from chrome network requests(form data or query string parameters) or postman headers key-value(in bulk edit style) to json format.

For example:
key:value pairs

platform:2
limit:10
start_time:1521561600
end_time:1522080000
offset:0

to json format

{
  "platform": "2",
  "limit": "10",
  "start_time": "1521561600",
  "end_time": "1522080000",
  "offset": "0"
}

It can be parsed (converted to json) using the help of this npm athena-struct-parser package.

For more information about the package -- https://www.npmjs.com/package/athena-struct-parser

Sample Nodejs Code

var parseStruct =require('athena-struct-parser') ;
var str = '{description=Check the Primary key count of TXN_EVENT table in Oracle, datastore_order=1, zone=yellow, aggregation_type=count, updatedcount=0, updatedat=[2021-06-09T02:03:20.243Z]}'
var parseObj = parseStruct(str)
console.log(parseObj);

Sample string with key=value format taken

   {description=Check the Primary key count of TXN_EVENT table in Oracle, datastore_order=1, zone=yellow, aggregation_type=count, updatedcount=0, updatedat=[2021-06-09T02:03:20.243Z]}

Result Parsed output

{
  description: 'Check the Primary key count of TXN_EVENT table in Oracle',
  datastore_order: '1',
  zone: 'yellow',
  aggregation_type: 'count',
  updatedcount: '0',
  updatedat: [ '2021-06-09T02:03:20.004Z' ]
}

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