JavaScript函数及运算符 -- 笔记 - 图2review0518

  1. <!DOCTYPE html>
  2. <html lang="en">
  3. <head>
  4.     <meta charset="UTF-8">
  5.     <title>review0518</title>
  6.     <script type="text/javascript">
  7.         // var n = 9;//全局变量
  8.         // function fun1(){
  9.         //     var n1 = 5;//局部变量
  10.         //     n = 12;//全局变量
  11.         // }
  12.         // function fun2(){
  13.         //     n = n - 1;
  14.         // }
  15.         // function fun3(){
  16.         //     console.log(n);//11
  17.         //     console.log(n1);//报错
  18.         // }
  19.         // fun1();
  20.         // fun2();
  21.         // fun3();
  23.         var x = 2;
  24.         var y = 3;
  25.         var z = 1;
  26.         var flag = x < 10 || y < 5|| z > 10;
  27.         console.log(flag);//true
  29.         var num1 = 10,
  30.             num2 = 5,
  31.             num3 = ++num1 + num2;
  32.             console.log(num1);//11
  33.             console.log(num3);//16
  35.         var num1 = 10,
  36.             num2 = 5,
  37.             num3 = num1++ + num2;
  38.             console.log(num1);//11
  39.             console.log(num3);//15
  41.         var x1 = 20;
  42.         var x2 = 30;
  43.         var x3 = --x1 + x2--;
  44.         console.log(x1);//19
  45.         console.log(x2);//29
  46.         console.log(x3);//49
  48.         var a = 10;
  49.         var b = 20;
  50.         var str = 'hello ';
  51.         a += 5;//a = a + 4
  52.         b %= 4;
  53.         str += 'world';
  54.         console.log(a);//15
  55.         console.log(b);//0
  56.         console.log(str);// hello world
  58.         var x = 10;
  59.         var y = '10';
  60.         var z = x === y;
  61.         console.log(z);//false
  63.         console.log(null == undefined);//true
  64.         console.log(null === undefined);//flase
  66.         var score = 95;
  67.         var str;
  68.         if (score > 100 || score < 0) {
  69.             str = '分数错误';
  70.         } else if (score == 100) {
  71.             str = '满分'; //成绩是100分，显示满分
  72.         } else if (score >= 90 && score < 100) {
  73.             str = '优秀'; //成绩大于等于90，显示优秀
  74.         } else if (score >= 70 && score < 90) {
  75.             str = '良好'; //成绩大于等于70，显示良好
  76.         } else if (score >= 60 && score < 70) {
  77.             str = '及格'; //成绩大于等于60分，显示及格
  78.         } else {
  79.             str = '不及格'; //否则，不及格
  80.         }
  81.         document.write(str);
  82.     </script>
  83. </head>
  84. <body>
  86. </body>
  87. </html>