Sorting an associative array in ascending order - JavaScript

In JavaScript, you can sort an array of objects (associative array) in ascending order using the sort() method with a custom comparison function.

Suppose we have an array of objects like this:

const people = [
    {"id":1, "name":"Andrew", "age":30, "gender":"m", "category":"G"},
    {"id":2, "name":"Brandon", "age":25, "gender":"m", "category":"G"},
    {"id":3, "name":"Christine", "age":20, "gender":"m", "category":"G"},
    {"id":4, "name":"Elena", "age":29, "gender":"W", "category":"M"}
];

We need to sort this array by the age property in ascending order. The expected output should be:

[
    {"id":3, "name":"Christine", "age":20, "gender":"m", "category":"G"},
    {"id":2, "name":"Brandon", "age":25, "gender":"m", "category":"G"},
    {"id":4, "name":"Elena", "age":29, "gender":"W", "category":"M"},
    {"id":1, "name":"Andrew", "age":30, "gender":"m", "category":"G"}
]

Using sort() with Custom Comparison Function

The sort() method modifies the original array. We pass a comparison function that returns:

• Negative value if first element should come before second
• Positive value if first element should come after second
• Zero if elements are equal

const people = [
    {"id":1, "name":"Andrew", "age":30, "gender":"m", "category":"G"},
    {"id":2, "name":"Brandon", "age":25, "gender":"m", "category":"G"},
    {"id":3, "name":"Christine", "age":20, "gender":"m", "category":"G"},
    {"id":4, "name":"Elena", "age":29, "gender":"W", "category":"M"}
];

// Comparison function for ascending order
const sorter = (a, b) => {
    return a.age - b.age;
};

// Function to sort array by age
const sortByAge = arr => {
    arr.sort(sorter);
};

sortByAge(people);
console.log(people);

[
  { id: 3, name: 'Christine', age: 20, gender: 'm', category: 'G' },
  { id: 2, name: 'Brandon', age: 25, gender: 'm', category: 'G' },
  { id: 4, name: 'Elena', age: 29, gender: 'W', category: 'M' },
  { id: 1, name: 'Andrew', age: 30, gender: 'm', category: 'G' }
]

Alternative Approaches

You can also write the sorting logic more concisely:

const people2 = [
    {"id":1, "name":"Andrew", "age":30, "gender":"m", "category":"G"},
    {"id":2, "name":"Brandon", "age":25, "gender":"m", "category":"G"},
    {"id":3, "name":"Christine", "age":20, "gender":"m", "category":"G"},
    {"id":4, "name":"Elena", "age":29, "gender":"W", "category":"M"}
];

// Direct inline comparison
people2.sort((a, b) => a.age - b.age);
console.log(people2);

[
  { id: 3, name: 'Christine', age: 20, gender: 'm', category: 'G' },
  { id: 2, name: 'Brandon', age: 25, gender: 'm', category: 'G' },
  { id: 4, name: 'Elena', age: 29, gender: 'W', category: 'M' },
  { id: 1, name: 'Andrew', age: 30, gender: 'm', category: 'G' }
]

Sorting by Different Properties

You can sort by any property using the same approach:

const people3 = [
    {"id":1, "name":"Andrew", "age":30, "gender":"m", "category":"G"},
    {"id":2, "name":"Brandon", "age":25, "gender":"m", "category":"G"},
    {"id":3, "name":"Christine", "age":20, "gender":"m", "category":"G"},
    {"id":4, "name":"Elena", "age":29, "gender":"W", "category":"M"}
];

// Sort by name alphabetically
people3.sort((a, b) => a.name.localeCompare(b.name));
console.log("Sorted by name:", people3[0].name, people3[1].name);

Sorted by name: Andrew Brandon

Key Points

• The sort() method modifies the original array
• For numbers: use (a, b) => a.property - b.property for ascending order
• For strings: use (a, b) => a.property.localeCompare(b.property)
• For descending order: reverse the comparison (a, b) => b.property - a.property

Conclusion

Use the sort() method with a custom comparison function to sort arrays of objects by any property. The pattern (a, b) => a.property - b.property provides ascending numeric sorting.