The accepted answer does not work for me for nested objects for some reason. This led me to code up my own. As it's late 2019 when I write this, there are a few more options available within the language.
Update: I believe David Furlong's answer is a preferable approach to my earlier attempt, and I have riffed off that. Mine relies on support for Object.entries(...), so no Internet Explorer support.
function normalize(sortingFunction) {
return function(key, value) {
if (typeof value === 'object' && !Array.isArray(value)) {
return Object
.entries(value)
.sort(sortingFunction || undefined)
.reduce((acc, entry) => {
acc[entry[0]] = entry[1];
return acc;
}, {});
}
return value;
}
}
JSON.stringify(obj, normalize(), 2);
--
KEEPING THIS OLDER VERSION FOR HISTORICAL REFERENCE
I found that a simple, flat array of all keys in the object will work. In almost all browsers (not Edge or Internet explorer, predictably) and Node 12+ there is a fairly short solution now that Array.prototype.flatMap(...) is available. (The lodash equivalent would work too.) I have only tested in Safari, Chrome, and Firefox, but I see no reason why it wouldn't work anywhere else that supports flatMap and standard JSON.stringify(...).
function flattenEntries([key, value]) {
return (typeof value !== 'object')
? [ [ key, value ] ]
: [ [ key, value ], ...Object.entries(value).flatMap(flattenEntries) ];
}
function sortedStringify(obj, sorter, indent = 2) {
const allEntries = Object.entries(obj).flatMap(flattenEntries);
const sorted = allEntries.sort(sorter || undefined).map(entry => entry[0]);
return JSON.stringify(obj, sorted, indent);
}
With this, you can stringify with no 3rd-party dependencies and even pass in your own sort algorithm that sorts on the key-value entry pairs, so you can sort by key, payload, or a combination of the two. Works for nested objects, arrays, and any mixture of plain old data types.
const obj = {
"c": {
"z": 4,
"x": 3,
"y": [
2048,
1999,
{
"x": false,
"g": "help",
"f": 5
}
]
},
"a": 2,
"b": 1
};
console.log(sortedStringify(obj, null, 2));
Prints:
{
"a": 2,
"b": 1,
"c": {
"x": 3,
"y": [
2048,
1999,
{
"f": 5,
"g": "help",
"x": false
}
],
"z": 4
}
}
If you must have compatibility with older JavaScript engines, you could use these slightly more verbose versions that emulate flatMap behavior. Client must support at least ES5, so no Internet Explorer 8 or below.
These will return the same result as above.
function flattenEntries([key, value]) {
if (typeof value !== 'object') {
return [ [ key, value ] ];
}
const nestedEntries = Object
.entries(value)
.map(flattenEntries)
.reduce((acc, arr) => acc.concat(arr), []);
nestedEntries.unshift([ key, value ]);
return nestedEntries;
}
function sortedStringify(obj, sorter, indent = 2) {
const sortedKeys = Object
.entries(obj)
.map(flattenEntries)
.reduce((acc, arr) => acc.concat(arr), [])
.sort(sorter || undefined)
.map(entry => entry[0]);
return JSON.stringify(obj, sortedKeys, indent);
}
