Explain the sorting method of array Array. sort of in detail

Array sort sorting

sort comparison times, sort usage, sort commonly used

Describe

The method sort () sorts the array elements on the original array, that is, no new array copy is created when sorting. If the method sort () is called without parameters, the elements in the array are sorted alphabetically (more precisely, in character encoding order). To achieve this point, you should first convert all the elements of the array to strings (if necessary) for comparison.

If you want to sort in another order, you must provide a comparison function that compares two values and returns a number indicating the relative order of the two values. The comparison function should have two parameters, a and b, and the return value is as follows:

If, by your criteria, a is less than b, a should appear before b in the sorted array, returning a value less than 0.

If a equals b, 0 is returned.

If a is greater than b, a value greater than 0 is returned.

Note that the elements of undefined in the array are arranged at the end of the array. This is true even if you provide a custom sorting function, because the undefined value will not be passed to the orderfunc you provide.

The sort () method of an array in JavaScript is primarily used to sort the elements of an array. The sort () method has one optional parameter. However, this parameter must be a function. When an array calls the sort () method, the elements in the array are sorted alphabetically (in character encoding order) if no arguments are passed. If you want to sort according to other criteria, you need to pass a parameter as a function, which compares two values and returns a number indicating the relative order of the two values.

1. Sort the number array from small to large.

Code:

var arr = [22,12,3,43,56,47,4];
arr.sort();
console.log(arr); // [12, 22, 3, 4, 43, 47, 56]
arr.sort(function (m, n) {
 if (m < n) return -1
 else if (m > n) return 1
 else return 0
});
console.log(arr); // [3, 4, 12, 22, 43, 47, 56]

2. Perform case-insensitive alphabetical sorting of string arrays.

Code:

var arr = ['abc', 'Def', 'BoC', 'FED'];
console.log(arr.sort()); // ["BoC", "Def", "FED", "abc"]
console.log(arr.sort(function(s, t){
 var a = s.toLowerCase();
 var b = t.toLowerCase();
 if (a < b) return -1;
 if (a > b) return 1;
 return 0;
})); // ["abc", "BoC", "Def", "FED"]

3. To sort the array containing objects, it is required to arrange them in the order from big to small according to the age in the objects

Code:

var arr = [{'name': ' Zhang 3', age: 26},{'name': ' Li 4', age: 12},{'name': ' Wang 5', age: 37},{'name': ' Zhao 6', age: 4}];
var objectArraySort = function (keyName) {
 return function (objectN, objectM) {
 var valueN = objectN[keyName]
 var valueM = objectM[keyName]
 if (valueN < valueM) return 1
 else if (valueN > valueM) return -1
 else return 0
 }
}
arr.sort(objectArraySort('age'))
console.log(arr) // [{'name': ' Wang 5', age: 37},{'name': ' Zhang 3', age: 26},{'name': ' Li 4', age: 12},{'name': ' Zhao 6', age: 4}]