Sorting multiple array elements alphabetically-CodePudding

I was wondering if there was a better or smarter way of sorting objects in JavaScript when sorting for multiple items?

For example, if I have the following JSON:

json = [
 { "type": "car",   "year": 2007, "origin": "AUS" },
 { "type": "truck", "year": 2021, "origin": "USA" },
 { "type": "car",   "year": 2004, "origin": "CA"  },
 { "type": "bike",  "year": 2016, "origin": "UK"  },
 { "type": "truck", "year": 2020, "origin": "CA"  },
 { "type": "bike",  "year": 2000, "origin": "AUS" }
]

If I wanted to sort it by type then year how would I do that in the same .sort function?

I've currently got it doing one, then the other - but when I try to combine them it doesn't seem to output correctly:

// one after other
json.sort( ( a, b ) => {
 a = a.type.toLowerCase();
 b = b.type.toLowerCase();
 return a < b ? -1 : a > b ? 1 : 0;
})
.sort( ( a, b ) => {
 a = a.year;
 b = b.year;
 return a < b ? -1 : a > b ? 1 : 0;
});

Returning:

[
 { "type": "bike",  "year": 2000, "origin": "AUS" },
 { "type": "car",   "year": 2004, "origin": "CA"  },
 { "type": "car",   "year": 2007, "origin": "AUS" },
 { "type": "bike",  "year": 2016, "origin": "UK"  },
 { "type": "truck", "year": 2020, "origin": "USA" },
 { "type": "truck", "year": 2021, "origin": "CA"  }
]

When it should return (all the types together, then by year):

[
 { "type": "bike",  "year": 2000, "origin": "AUS" },
 { "type": "bike",  "year": 2016, "origin": "UK"  },
 { "type": "car",   "year": 2004, "origin": "CA"  },
 { "type": "car",   "year": 2007, "origin": "AUS" },
 { "type": "truck", "year": 2020, "origin": "USA" },
 { "type": "truck", "year": 2021, "origin": "CA"  }
]

CodePudding user response：

In the sort callback, compare the items' type property. If one is lexographically greater/smaller, sort it before/after the other item accordingly.

Otherwise, you can return the result after subtracting the two items' year property:

const arr = [
 { "type": "car",   "year": 2007, "origin": "AUS" },
 { "type": "truck", "year": 2021, "origin": "USA" },
 { "type": "car",   "year": 2004, "origin": "CA"  },
 { "type": "bike",  "year": 2016, "origin": "UK"  },
 { "type": "truck", "year": 2020, "origin": "CA"  },
 { "type": "bike",  "year": 2000, "origin": "AUS" }
]

const sorted = arr.sort((a,b) => a.type.localeCompare(b.type) || a.year - b.year)

console.log(sorted)

^{Credit to DraganS}

If you don't want the comparison to be case-sensitive, you can set localeCompare's sensitivity option to accent:

const arr = [
 { "type": "car",   "year": 2007, "origin": "AUS" },
 { "type": "truck", "year": 2021, "origin": "USA" },
 { "type": "car",   "year": 2004, "origin": "CA"  },
 { "type": "bike",  "year": 2016, "origin": "UK"  },
 { "type": "truck", "year": 2020, "origin": "CA"  },
 { "type": "bike",  "year": 2000, "origin": "AUS" }
]

const sorted = arr.sort((a,b) => a.type.localeCompare(b.type, undefined, {sensitivity:'accent'}) || a.year - b.year)

console.log(sorted)

CodePudding user response：

You can do this with one sort by first checking if the types are equal. If so, sort on the date. If not, sort on the type.

const json = [
 { "type": "car",   "year": 2007, "origin": "AUS" },
 { "type": "truck", "year": 2021, "origin": "USA" },
 { "type": "car",   "year": 2004, "origin": "CA"  },
 { "type": "bike",  "year": 2016, "origin": "UK"  },
 { "type": "truck", "year": 2020, "origin": "CA"  },
 { "type": "bike",  "year": 2000, "origin": "AUS" }
]

// one after other
json.sort( ( a, b ) => {
 a = a.type.toLowerCase();
 b = b.type.toLowerCase();
 if (a === b) {
   return a.year - b.year;
 }
 return a < b ? -1 : 1;
});

console.log(json);

CodePudding user response：

If you do one sort followed by a different sort, the final sort overrides any previous sort.

Combine them into the same lambda


json.sort( ( a, b ) => {
 aType = a.type.toLowerCase();
 bType = b.type.toLowerCase();
 aYear = a.year;
 bYear = b.year;
 return aType < bType 
        ? -1 
        : aType > bType 
           ? 1 
           : aYear < bYear
              ? -1
              : aYear > bYear
                 ? 1
                 : 0;
})

Though this has gotten pretty unreadable. You can have multiple comparison functions:

let compareByType = (a, b) => {
     aType = a.type.toLowerCase();
     bType = b.type.toLowerCase();
     return (aType<bType) ? -1 : (aType>bType ? 1 : 0);
}

let compareByYear = (a,b) => {
     return a.year - b.year;
}

json.sort(
    (a, b) => {
       let s = compareByType(a, b);
       if(s !== 0) {
          return s;
       } else {
           return compareByYear(a, b);
       }
    }
);