检查数组是下降,升序还是未排序？

Question

我刚刚开始使用javascript进行编程,我需要练习一些问题来获得带有代码构建逻辑的EXP.我得到了这个问题的功课,但由于某种原因我无法使它工作,即使它对我来说似乎是"逻辑".检查数组是使用循环降序,升序还是不分类.

我只是一个菜鸟所以请尽量帮助我解决这个问题,因为我只能在学习中循环(这是我写的代码:

        var array = [1, 2, 3, 7 ];
        var d = 0;
        var c =0 ;
        var b = 1;
        var a = 0;
        for (var i = 1; i <= array.length; i++)
            {
                if (array[c]<array[b] && a!== -1  ){
                   d = -1;
                   c =c+1;
                   b = b+1;
                   if(c==array.length){
                    console.log("asc");
                     break;
                   }else{
                     continue;
                }

                } else if (array[c]>array[b] && d!==-1 ){
                           a = -1;
                           d= d+1;
                           b = b+1;
                    if(i=array.length){
                    console.log("dsc");
                    break;
               }else{continue;}

               } else{

                    console.log("unsorted array");
                    break;
                }

            }

Answer 1

“使用循环检查数组是否按降序、升序或未排序”

// define the array
var array = [1,2,3,7];

// keep track of things
var isDescending = true;
var isAscending = true;

// we're looking ahead; loop from the first element to one before the last element
for (var i=0, l=array.length-1; i<l; i++)
{

   ////////////////////////////////////////////////////////////

   // log to the console to show what's happening for each loop iteration

   // this is the ith iteration 
   console.log("loop iteration %s", i);

   // breaking isDescending down:
   // is this value greater than the next value?
   console.log("A: (%s > %s) = %s", array[i], array[i+1], (array[i] > array[i+1]));

   // have all values been descending so far?
   console.log("B: isDescending: %s", isDescending);

   // if this value is greater than the next and all values have been descending so far, isDescending remains true. Otherwise, it's set to false.
  console.log("are A and B both true? %s", (isDescending && (array[i] > array[i+1])));

   // add a line break for clarity
   console.log("");

   ////////////////////////////////////////////////////////////


   // true if this is greater than the next and all other so far have been true
   isDescending = isDescending && (array[i] > array[i+1]);

   // true if this is less than the next and all others so far have been true
   isAscending = isAscending && (array[i] < array[i+1]);

}

if (isAscending)
{
  console.log('Ascending');
}
else if (isDescending) 
{
  console.log('Descending');
}
else
{
  console.log('Not Sorted');
}

Answer 2

Array.prototype.every 将其谓词传递给索引,您可以使用该索引获取元素的前任:

function isAscending(arr) {
    return arr.every(function (x, i) {
        return i === 0 || x >= arr[i - 1];
    });
}

在这里,我们检查每个item(x)是否大于或等于它之前的项目(arr[i - 1])或它之前没有项目(i === 0).

翻转>=到<=了isDescending.