更新

2021-05-11 11:33:55 +08:00
parent 011d9328b0
commit c5f18c6051
32 changed files with 2011 additions and 26 deletions
--- a/teaching/lhj/kejian/js/yunsuanfu.html
+++ b/teaching/lhj/kejian/js/yunsuanfu.html
@@ -0,0 +1,35 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta http-equiv="X-UA-Compatible" content="IE=edge">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Document</title>
+    <script>
+        // var a=1
+        // function test(){
+        //     alert(a)  //undefined 
+        //     var a=2
+        //     alert(a)  //2
+        // }
+        // test()
+        // alert(a)  // 1 
+        // undefined 2 1
+
+        // alert(Boolean("non-empty string")) //true
+        // alert(Boolean(null)) //false
+        alert(alert(1)||2||alert(3)) //1
+        // alert(alert(1)&& alert(0)) //1
+
+// &&如果第一个是false就不走第二个。
+// alert没有返回值，所以布尔值是false
+// ||是第一个true不走第二个
+
+
+
+    </script>
+</head>
+<body>
+    
+</body>
+</html>