JavaScript日期函数和数组 -- 笔记 - 图2review0520

  1. <!DOCTYPE html>
  2. <html lang="en">
  3. <head>
  4.     <meta charset="UTF-8">
  5.     <title>review0520</title>
  6.     <script type="text/javascript">
  7.         //日期函数 自定义一个函数来实现日期获取
  8.         function fun_fmtDate(){
  9.             var d1 = new Date();
  10.             var yyyy = d1.getFullYear();
  11.             var mm=d1.getMonth()+1;
  12.             var dd=d1.getDate();
  13.             var hh=d1.getHours();
  14.             var mi=d1.getMinutes();
  15.             var ss=d1.getSeconds();
  16.             var time=yyyy+"-"+mm+"-"+dd+" "+hh+":"+mi+":"+ss;
  17.             return time;
  18.         }
  19.         console.log(fun_fmtDate());
  21.         //数学函数 
  22.         var n = 16.65724;
  23.         console.log(Math.round(n));
  24.         //js中round只能取整数，不能保留小数，遵循四舍五入
  25.         console.log(n.toFixed(2));//小数点后两位
  26.         console.log(n.toFixed(0));//17
  27.         console.log(Math.min(2,6,81,1));//最小值
  28.         console.log(Math.max(2,6,81,1));//最大值
  29.         console.log(Math.abs(-3));//绝对值
  30.         console.log(Math.abs(5));//绝对值
  32.         var arrayObj = new Array(2,4,"a","y",8);
  33.         var arrayObj = [2,4,"a","y",8];
  34.         console.log(arrayObj);
  35.         console.log("数组arrayObj的长度为："+arrayObj.length);
  36.         console.log(arrayObj[0]);//2
  37.         console.log(arrayObj[4]);//8
  38.         console.log(arrayObj[5]);//undefined
  40.         for(var i in arrayObj){
  41.         // console.log(str);//获取的是索引值
  42.             console.log(arrayObj[i]);
  43.         }
  45.         var i;
  46.         var n=arrayObj.length;
  47.         for(i=0;i<n;i++){
  48.             console.log(arrayObj[i]);
  49.         }
  51.         var colors = new Array(3);
  52.         colors[0] = '#f00';
  53.         colors[1] = '#0f0';
  54.         colors[2] = '#00f';
  55.         console.log(colors.length);
  56.         console.log(colors);
  58.         var arr = ['a', 'b', 'c', 'd', 'e'];
  59.         arr[99] = 'z';
  60.         console.log(arr.length);
  62.         for (var i=0;i<arr.length;i++){
  63.             console.log(arr[i]);
  64.         }
  66.         var nums = [1, 2, 3, 4];
  67.         var sizes = nums.unshift(99, 66);
  68.         console.log(sizes);
  69.         console.log(nums);
  71.         var n = nums.pop();
  72.         console.log(n);//弹栈会返回元素值
  73.         console.log(nums);//此时被弹出的元素不在数组之中
  75.         var len = nums.push('3','4');
  76.         console.log(nums.length);
  77.         console.log(nums);//入栈往后加
  79.         var m = nums.shift();
  80.         console.log(nums);
  81.         console.log(m);//同理
  83.         var words = ['bor','sis','mom','dad'];
  84.         var wordsStr = words.join('-');
  85.         console.log(typeof(wordsStr));
  87.         nums.reverse();//返回数组
  88.         console.log(nums);
  90.         var arrDemo = [9,23,15,88,12];
  91.         arrDemo.sort(function(a,b){
  92.             return b-a;
  93.         });
  94.         console.log(arrDemo);
  96.         //拼接
  97.         var arr1 = ['a','b','c'],
  98.             arr2 = ['d','e'],
  99.             arr3;
  100.         arr3 = arr1.concat(arr2,['m','n'],arr2);
  101.         console.log(arr3);
  102.     </script>
  103. </head>
  104. <body>
  106. </body>
  107. </html>

review0521-1

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>数组面试题部分及补充内容</title>
    <script type="text/javascript">
        //面试题：实现b数组对a数组的拷贝，方法越多越好
        var a = [1,'yes',3], b;
        //1、slice()
        b = a.slice(0);
        console.log(b);
        console.log(typeof b);
        //2、数组遍历和push
        b = new Array();
        for (var i=0;i<a.length;i++){
            b.push(a[i]);
        }
        console.log(b);
        //3、concat
        b = [].concat(a);
        console.log(b);

        //charCodeAt()  返回字符串中的index位置字符的ascii
        var str = 'hello world';
        console.log(str.length);
        console.log(str[1]);
        console.log(str.charAt(4));
        console.log(str.charCodeAt(4));

        //Math.ceil(num)  向上取整
        var num1 = Math.round(189.99);
        console.log(num1);
        var num2 = Math.ceil(189.99);
        console.log(num2);
        var num3 = Math.round(189.09);
        console.log(num3);

        //Math.floor(num)  向下取整
        var num4 = Math.floor(189.99);
        console.log(num4);
        var num5 = Math.floor(189.09);
        console.log(num5);

        //Math.random()  0-1之间的随机数
        var randomNum = Math.random();
        console.log(randomNum);

        document.write('按F12 进入Console查看结果！')

        var arr = [1,2,3,4,5,6,7,8,9];
        var newArr = arr.slice(-6,8);
        console.log(newArr);
    </script>
</head>
<body>

</body>
</html>