How to sort array of objects in JavaScript based on definite attribute value?

Question

So I have this array of notification objects that has to be sorted in decreasing order of severity i.e. Error > Warning > Information.

Example:

var notificationArray = [ {
    code : "103",
    severity : "Error"
}, {
    code : "104",
    severity : "Information"
}, {
    code : "109",
    severity : "Error"
}, {
    code : "403",
    severity : "Warning"
}, {
    code : "510",
    severity : "Information"
}, {
    code : "114",
    severity : "Warning"
}, {
    code : "144",
    severity : "Error"
}, {
    code : "413",
    severity : "Warning"
} ];

What's the easiest way to make sure this array is always sorted based on severity?

P.S. There are other threads on sorting an array of objects but what I mostly found is unicode sorting and not sorting by comparing against a fixed value. Apologies if I posted a duplicate question.

“but I didn't find one that talks about sorting on attribute value (and not attribute itself)” – what else would you sort by, if not the value? — C3roe
– C3roe, Commented Mar 1, 2017 at 14:07

Nina Scholz · Accepted Answer · 2017-03-01 14:13:59Z

15

You could sort with an order object for the priority of severity.

var notificationArray = [{ code: "103", severity: "Error" }, { code: "104", severity: "Information" }, { code: "109", severity: "Error" }, { code: "403", severity: "Warning" }, { code: "510", severity: "Information" }, { code: "114", severity: "Warning" }, { code: "144", severity: "Error" }, { code: "413", severity: "Warning" }, { code: "131", severity: "Error"}],
    order = { Error: 1, Warning: 2, Information: 3 };

notificationArray.sort(function (a, b) {
    return order[a.severity] - order[b.severity];
});

console.log(notificationArray);

.as-console-wrapper { max-height: 100% !important; top: 0; }

edited Mar 1, 2017 at 14:13

answered Mar 1, 2017 at 14:07

Nina Scholz

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8 Comments

Weedoze Over a year ago

Would it not be better to define the order object outside the sort function ?

Nina Scholz Over a year ago

@Weedoze, better, hm. but why not.

baao Over a year ago

I've upvoted your other (same) answer so that we can use it as a dupe target for those frequent questions...

Lalit Over a year ago

@Nina, worked with the original set but then I introduced another {code: "131", severity: "Error"} in the array and tried to sort again. Didn't work!

Nina Scholz Over a year ago

@Weedoze, it uses the same reference, is suppose. it makes no difference, but some is local and the other global.

|

Alexandre Nicolas · Accepted Answer · 2017-03-01 14:09:02Z

Here a solution:

var errors = notificationArray.map(function(message) {
  return message.severity === 'Error';
});
var warnings = notificationArray.map(function(message) {
  return message.severity === 'Warning';
});
var infos = notificationArray.map(function(message) {
  return message.severity === 'Information';
});

var sortedMessage = errors.concat(warnings).concat(infos);

I don't know if it's faster then @NinaScholz solution, (perhaps it's more understable for you).

beta-developper · Accepted Answer · 2017-03-01 14:11:36Z

-1

For each severity, associate a priority

EX :

var severity = {
    information: 0
    warning : 1,
    error : 2, 
}

Then sort the array based on the priority of each severity

notificationArray.sort(function(a, b) {
    var p1 = severity[a.severity.toLowerCase()];
    var p2 = severity[b.severity.toLowerCase()];
    return p2 - p1;
});

answered Mar 1, 2017 at 14:11

beta-developper

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