odd:奇数 1%2 0,1,2,3,4
    even偶数 0,1,0,1,0

    1. <!DOCTYPE html>
    2. <html lang="en">
    3. <head>
    4.     <meta charset="UTF-8">
    5.     <meta name="viewport" content="width=device-width, initial-scale=1.0">
    6.     <title>Document</title>
    7. </head>
    8. <style>
    9.     /*
    10.     odd:奇数
    11.     even：偶数
    12.     */
    13.     li:nth-child(even){
    14.         background-color: pink;
    15.     }
    16.     li:nth-child(odd){
    17.         background-color: pink;
    18.     }
    19. </style>
    20. <body>
    21.     <ul>
    22.         <li>1</li>
    23.         <li>2</li>
    24.         <li>3</li>
    25.         <li>4</li>
    26.         <li>5</li>
    27.     </ul>
    28.     <script>
    29.         /*
    30.         1%2 0,1,2,3,4
    31.             0,1,0,1,0
    32.         */
    33.         var lis = document.getElementsByTagName("li");
    34.         for(var i=0;i<lis.length;i++){
    35.             if(i%2==0){
    36.                 lis[i].style.backgroundColor = "pink"
    37.             }else{
    38.                 lis[i].style.backgroundColor = "yellow"
    39.             }
    40.         }
    42.     </script>
    43. </body>
    44. </html>

    1.PNG