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Example Analysis of Sorting Usage of sort Function in JS

  • 2021-06-28 10:53:51
  • OfStack

This article gives an example of the sorting usage of the sort function in JS.Share it for your reference, as follows:

Recently, I have encountered an interview question about sorting. In order to improve my knowledge, here is a learning note 


<html>
<head>
<TITLE>class_obj_js_class</TITLE>
<script language=javaScript>
//sort()方法默认是按照ASCII码大小排序，看下面两个例子
function sortDemo(){
 var a, l;      // 声明变量。
 a = new Array("X" ,"y" ,"d", "Z", "v","m","r");
 l = a.sort();     // 排序数组。
 alert(l);
 return(l);      // 返回排序的数组。
}
//sortDemo();
function sortDemo2(){
  var arr = [50,200,3000];
  arr.sort();
  alert(arr);
}
//显示的结果为200、3000、50，因为是根据首字母2，3，5判断的
//sortDemo2();
//将上面的数字按照数字大小写排序，if条件是对大小的判断，因此就算对大小的排序
function testFunction(){
  var numArr = new Array(9,23,124);
  numArr.sort(function compare(a,b){
    if(a>b){
      return 1;//按照升序排列,即a排在b的后面
    }
    else
      return -1;
  });
  alert(numArr);
}
//testFunction();
//如果sort(sortfunction)中的sortfunction在a>b返回的值为真则是按照降序排列，反之按照升序排列
function testFunction2(){
  var numArr = new Array(9,124,23);
  numArr.sort(function compare(a,b){
    alert("a : " + a);
    alert("b : " + b);
    if(a > b){
      alert("a > b,返回正数");
      return -1;//按照降序排列，即a排在b的前面
    }
    else{
      alert("a < b,返回负数");
      return 1;
    }
  });
  alert(numArr);
}
//testFunction2();
/*要使数组的元素按先奇数后偶数的顺序排列，则若需a、b交换，仅当满足a是偶数且b是奇数条件即可，再按从小到大排序，仅当满足a、b均是奇数或偶数且a>b时即可
从下面的例子可以看出,根据if的条件就是需要排序的要求，返回的值大于0就可以了，就是对1次条件的排序*/
function testAdvance(){
  var a = [1, 7, 3, 9, 5, 6, 2, 8, 4];
  function f(a, b) {
    if (0 == a % 2 && 1 == b % 2) {
      return 1;//即对偶数和奇数排序
    }
    if ((1 == a % 2 && 1 == b % 2 || 0 == a % 2 && 0 == b % 2) && a > b) {
      return 1;//对奇数和偶数排序
    }
    return -1;
  }
 alert(a.sort(f));
}
//testAdvance();
//我们要做的就是写出if里面的条件，这个条件就是返回a、b需要交换的条件
//譬如：对var a=["a","A","B","b"];进行不分大小写并从大到小排序，仅当a.toString().toLowerCase() < b.toString().toLowerCase()时，交换a、b，所以用此填充if条件即可。
function testAdvance1(){
  var a=["a","A","B","b"];
  a.sort(function test(a,b){
    if(a.toString().toLowerCase() < b.toString().toLowerCase()){
      return 1;
    }
    else
      return -1;
  });
  alert(a);
}
testAdvance1();
</script>
<body >
</body>
</html>

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I hope that the description in this paper will be helpful to everyone's JavaScript program design.

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