不同的浏览器对他的实现是不一样的
主要是归并排序和快速排序
谷歌V8源码:(说实话我只能看懂有快速排序)
function ArraySort(comparefn) {
// In-place QuickSort algorithm.
// For short (length <= 22) arrays, insertion sort is used for efficiency.
var custom_compare = IS_FUNCTION(comparefn);
function Compare(x,y) {
// Assume the comparefn, if any, is a consistent comparison function.
// If it isn't, we are allowed arbitrary behavior by ECMA 15.4.4.11.
if (x === y) return 0;
if (custom_compare) {
// Don't call directly to avoid exposing the builtin's global object.
return comparefn.call(null, x, y);
}
if (%_IsSmi(x) && %_IsSmi(y)) {
return %SmiLexicographicCompare(x, y);
}
x = ToString(x);
y = ToString(y);
if (x == y) return 0;
else return x < y ? -1 : 1;
};
function InsertionSort(a, from, to) {
for (var i = from + 1; i < to; i++) {
var element = a[i];
// Pre-convert the element to a string for comparison if we know
// it will happen on each compare anyway.
var key =
(custom_compare || %_IsSmi(element)) ? element : ToString(element);
// place element in a[from..i[
// binary search
var min = from;
var max = i;
// The search interval is a[min..max[
while (min < max) {
var mid = min + ((max - min) >> 1);
var order = Compare(a[mid], key);
if (order == 0) {
min = max = mid;
break;
}
if (order < 0) {
min = mid + 1;
} else {
max = mid;
}
}
// place element at position min==max.
for (var j = i; j > min; j--) {
a[j] = a[j - 1];
}
a[min] = element;
}
}
function QuickSort(a, from, to) {
// Insertion sort is faster for short arrays.
if (to - from <= 22) {
InsertionSort(a, from, to);
return;
}
var pivot_index = $floor($random() * (to - from)) + from;
var pivot = a[pivot_index];
// Pre-convert the element to a string for comparison if we know
// it will happen on each compare anyway.
var pivot_key =
(custom_compare || %_IsSmi(pivot)) ? pivot : ToString(pivot);
// Issue 95: Keep the pivot element out of the comparisons to avoid
// infinite recursion if comparefn(pivot, pivot) != 0.
a[pivot_index] = a[from];
a[from] = pivot;
var low_end = from; // Upper bound of the elements lower than pivot.
var high_start = to; // Lower bound of the elements greater than pivot.
// From low_end to i are elements equal to pivot.
// From i to high_start are elements that haven't been compared yet.
for (var i = from + 1; i < high_start; ) {
var element = a[i];
var order = Compare(element, pivot_key);
if (order < 0) {
a[i] = a[low_end];
a[low_end] = element;
i++;
low_end++;
} else if (order > 0) {
high_start--;
a[i] = a[high_start];
a[high_start] = element;
} else { // order == 0
i++;
}
}
QuickSort(a, from, low_end);
QuickSort(a, high_start, to);
}
var old_length = ToUint32(this.length);
if (old_length < 2) return this;
%RemoveArrayHoles(this);
var length = ToUint32(this.length);
// Move undefined elements to the end of the array.
for (var i = 0; i < length; ) {
if (IS_UNDEFINED(this[i])) {
length--;
this[i] = this[length];
this[length] = void 0;
} else {
i++;
}
}
QuickSort(this, 0, length);
// We only changed the length of the this object (in
// RemoveArrayHoles) if it was an array. We are not allowed to set
// the length of the this object if it is not an array because this
// might introduce a new length property.
if (IS_ARRAY(this)) {
this.length = old_length;
}
return this;
}
不过记住
a-b:从小到大
b-a:从大到小
用比较函数return可以比较字符串类型的数字 确保 “5” < “15” 等类似的情况
var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.sort(); // 对 fruits 中的元素进行排序
console.log(fruits);
var nums = [1, 5, 8, 9, 4, 6, 7, 3];
nums.sort();
console.log(nums);
用比较函数确保字符串型的数字比较正确
var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.sort(); // 对 fruits 中的元素进行排序
console.log(fruits);
var nums = [1, 5, 8, 9, 4, 6, 7, 3];
nums.sort(); //默认升序
nums.sort(function(a, b) {
return a - b; // 升序
})
nums.sort(function(a, b) {
return b - a; //降序
})
console.log(nums);
这样之后就差不多了吧