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js中sort()方法的源码,该怎么解决

热度:436   发布时间:2012-03-09 16:54:57.0
js中sort()方法的源码
js中sort()方法的源码,帮我分析出来,谢谢,不是方法的运用,是封装好的sort()方法的代码,谢谢

------解决方案--------------------
v8里面的。


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 {
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