Array reordering method in JS

1. There are already two methods in the array that can be used directly to reorder: reverse() and sort(). The return value of the

reverse() and sort() methods is the sorted array. The reverse() method will reverse the order of the array items:

var values=[1,2,3,4,5];
values.reverse();
alert(values); //5,4,3,2,1

By default, the sort() method sorts the array in ascending order, and the sort() method will call the toString() transformation method of each array item, Then compare the strings to determine how to sort them. Even though each item in the array is a numeric value, the sort() method compares strings:

var values = [0,1,5,10,15];
values.sort();
alert(values); //0,1,10,15,5

Therefore, the sort() method can receive a comparison function as a parameter.

function compare(value1,value2){
if (value1 < value2){
return -1;
}else if (value1 > value2){
return 1;
}else{
return 0;
}
}

This comparison function can be applied to most data types, just pass it as a parameter to the sort() method:

var values = [0,1,3,7,9,15];
values.sort(compare);
alert(values); //0,1,3,7,9,15

Descending sort can also be produced through the comparison function, just Just exchange the return value of the function:

function compare (value1, value2){
if (value1<value2){
return 1;
}else if {
return -1;
}else{
return 0;
}
}

The sorting conditions of the sort() function are:

parameter is greater than 0, two adjacent elements of arr exchange positions;

parameter is less than 0, two adjacent elements of arr The elements do not exchange positions; the

parameter is equal to 0, and the two adjacent elements of arr are equal in size; so the compare custom function must return a numerical value.

2. For numerical types or the valueOf() method will return the object type of numerical type.

A simpler comparison function can be used. This function only needs the second value minus the first value.

function compare (value1,value2){
return value2 - value1;
}