Ways of sorting an array of objects

sorting-array-of-objects.js

// Ways to sort an array of objects
var arr = [{"member_id":"40323","person_id":"24709","name":"Bridget Phillipson","party":"Labour","constituency":"Houghton and Sunderland South","office":[]},{"member_id":"40636","person_id":"11592","name":"Sharon Hodgson","party":"Labour","constituency":"Washington and Sunderland West","office":[]},{"member_id":"40592","person_id":"24710","name":"Julie Elliott","party":"Labour","constituency":"Sunderland Central","office":[]},{"member_id":"40068","person_id":"13814","name":"Naomi Long","party":"Alliance","constituency":"Belfast East","office":[]},{"member_id":"40428","person_id":"13852","name":"Ian Paisley Jnr","party":"DUP","constituency":"North Antrim"},{"member_id":"40653","person_id":"10858","name":"Pat Doherty","party":"Sinn Fein","constituency":"West Tyrone"},{"member_id":"40434","person_id":"11003","name":"Kevan Jones","party":"Labour","constituency":"North Durham","office":[]},{"member_id":"40606","person_id":"10626","name":"Steve Webb","party":"Liberal Democrat","constituency":"Thornbury and Yate","office":[]},{"member_id":"40196","person_id":"24711","name":"Jenny Chapman","party":"Labour","constituency":"Darlington","office":[]},{"member_id":"40350","person_id":"10172","name":"Jeffrey M Donaldson","party":"DUP","constituency":"Lagan Valley"},{"member_id":"40045","person_id":"11323","name":"Hywel Williams","party":"Plaid Cymru","constituency":"Arfon","office":[]},{"member_id":"40347","person_id":"24713","name":"Chris Skidmore","party":"Conservative","constituency":"Kingswood"},{"member_id":"40129","person_id":"11461","name":"Charles Walker","party":"Conservative","constituency":"Broxbourne"}]


// Sort by id string - parsed to integer

arr.sort(function(a, b) {
	// a - b for integer values
	return parseInt(a.member_id, 10) - parseInt(b.member_id, 10);
});


// Sort alphabetically by name (or any other string property)

arr.sort(function(a, b) {

	var a = a.name.toLowerCase(), b = b.name.toLowerCase();

	// if a less than b, sort a to lower index than b
	if (a < b) {
		return -1;
	}
	// if b greater than a, sort b to a lower index than a
	if (a > b) {
		return 1;
	}
	// if a === b, leave unchanged
	return 0;
	
	// or using ternary operator
	// return  a < b  ? -1 : a > b  ? 1 : 0;
	
});


// Using .map - runs function over each element in array
// and constructs new array from transformed values

var map = arr.map(function(e, i) { 
  // extracts constituency value from each object in array and gives it an index 
	return { index: i, value: e.constituency.toLowerCase() }
})

// map = [ {index: 0, value: "houghton and sunderland south"}, {index: 1, value: "washington and sunderland west"}, { etc

// now sort map into order
map.sort(function (a,b) {
	if (a.value < b.value) {
		return -1;
	}
	if (a.value > b.value) {
		return 1;
	}
	return 0;
});

// map ordered by value not index
// map = [ {index: 10, value: "arfon"}, {index: 3, value: "belfast east"}, { etc


// use map to order the original array of objects put it in a new variable, sorted_array
var sorted_array = map.map(function(e) {
  
  // the first item in map has index:10 so the first item in the sorted_array will be arr[10]
  // which is {member_id: "40045", person_id: "11323", name: "Hywel Williams", party: "Plaid Cymru", constituency: "Arfon"…}
  
	return arr[e.index];
})