JavaScript sort array by multiple (number) fields
How can I implement a
ORDER BY sort1 DESC, sort2 DESC
logic in an JSON array like such:
var items = '[
{
"sort1": 1,
"sort2": 3,
"name" : "a",
},
{
"sort1": 1,
"sort2": 2,
"name" : "b",
},
{
"sort1": 2,
"sort2": 1,
"name" : "c",
}
]';
resulting in the new order :
b,a,c
You should design your sorting function accordingly:
items.sort(function(a, b) {
return a.sort1 - b.sort1 || a.sort2 - b.sort2;
});
(because || operator has lower precedence than - one, it's not necessary to use parenthesis here).
The logic is simple: if a.sort1 - b.sort1 expression evaluates to 0 (so these properties are equal), it will proceed with evaluating || expression - and return the result of a.sort2 - b.sort2 .
As a sidenote, your items is actually a string literal, you have to JSON.parse to get an array:
const itemsStr = `[{
"sort1": 1,
"sort2": 3,
"name": "a"
},
{
"sort1": 1,
"sort2": 2,
"name": "b"
},
{
"sort1": 2,
"sort2": 1,
"name": "c"
}
]`;
const items = JSON.parse(itemsStr);
items.sort((a, b) => a.sort1 - b.sort1 || a.sort2 - b.sort2);
console.log(items);You can avoid hardcoding by create a general function
function sortByMultipleKey(keys) {
return function(a, b) {
if (keys.length == 0) return 0; // force to equal if keys run out
key = keys[0]; // take out the first key
if (a[key] < b[key]) return -1; // will be 1 if DESC
else if (a[key] > b[key]) return 1; // will be -1 if DESC
else return sortByMultipleKey(keys.slice(1))(a, b);
}
}
Running
items.sort(sortByMultipleKey(['sort1', 'sort2']));
will have you
[ { sort1: 1, sort2: 2, name: 'b' },
{ sort1: 1, sort2: 3, name: 'a' },
{ sort1: 2, sort2: 1, name: 'c' } ]
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