Is there a way to sort/order keys in JavaScript objects?
Yes, there is. Not within ECMAScript standard, but supported across browsers and Node.js, and apparently stable. See https://stackoverflow.com/a/23202095/645715.
EDIT: This returns an object in which the keys are ordered. You can use Object.keys(...)
to get the ordered keys from the object.
Why worry about object key order? The difference can matter in some applications, such as parsing XML with xml2js which represents XML as nested objects, and uses XML tags as hash keys.
There are a couple notes:
- keys that look like integers appear first and in numeric order.
- keys that look like strings appear next and in insertion order.
- this order is reported by
Object.keys(obj)
- the order as reported by
for (var key in obj) {...}
may differ in Safari, Firefox
The function returns an object with sorted keys inserted in alphabetic order:
function orderKeys(obj, expected) {
var keys = Object.keys(obj).sort(function keyOrder(k1, k2) {
if (k1 < k2) return -1;
else if (k1 > k2) return +1;
else return 0;
});
var i, after = {};
for (i = 0; i < keys.length; i++) {
after[keys[i]] = obj[keys[i]];
delete obj[keys[i]];
}
for (i = 0; i < keys.length; i++) {
obj[keys[i]] = after[keys[i]];
}
return obj;
}
Here's a quick test:
var example = {
"3": "charlie",
"p:style": "c",
"berries": "e",
"p:nvSpPr": "a",
"p:txBody": "d",
"apples": "e",
"5": "eagle",
"p:spPr": "b"
}
var obj = orderKeys(example);
this returns
{ '3': 'charlie',
'5': 'eagle',
apples: 'e',
berries: 'e',
'p:nvSpPr': 'a',
'p:spPr': 'b',
'p:style': 'c',
'p:txBody': 'd' }
You can then get the ordered keys as:
Object.keys(obj)
Which returns
["3", "5", "apples", "berries", "p:nvSpPr", "p:spPr", "p:style", "p:txBody"]
Not within the object itself: the property collection of an object is unordered.
One thing you could do is use Object.keys()
, and sort the Array, then iterate it.
Object.keys(data)
.sort()
.forEach(function(v, i) {
console.log(v, data[v]);
});
Patches (implementations) for browsers that do not support ECMAScript 5th edition:
Object.keys
Array.forEach
here's a nice functional solution:
basically,
- extract the keys into a list with
Object.keys
sort
the keys- reduce list back down to an object to get desired result
ES5 Solution:
not_sorted = {b: false, a: true};
sorted = Object.keys(not_sorted)
.sort()
.reduce(function (acc, key) {
acc[key] = not_sorted[key];
return acc;
}, {});
console.log(sorted) //{a: true, b: false}
ES6 Solution:
not_sorted = {b: false, a: true}
sorted = Object.keys(not_sorted)
.sort()
.reduce((acc, key) => ({
...acc, [key]: not_sorted[key]
}), {})
console.log(sorted) //{a: true, b: false}