1 <!DOCTYPE html>
2 <html lang="en">
3 <head>
4 <meta charset="UTF-8">
5 <title></title>
6 <script type="text/javascript">
7 function test(){
8 var obj={name:"哈喽"};
9 var t1=!!obj.name;//等效于var test=o.flag||false;
10 console.log(t1);//true
11 var t2=obj.name||false;
12 console.log(t2);//哈喽
13
14 var obj1={name:""};
15 var t3 = obj1.name||false;
16 console.log((!!obj1.name)+""+t3);//false
17
18 var obj2={name:undefined};
19 var t4 = obj2.name||false;
20 console.log((!!obj2.name)+""+t4);//false
21
22 var obj3={name:null};
23 var t5 = obj3.name||false;
24 console.log((!!obj3.name)+""+t5);//false
25
26 var obj4={name:" "};
27 var t6 = obj4.name||false;
28 console.log((!!obj4.name)+""+t6);//true 空格
29
30 var obj5={};
31 console.log(!!obj5.name);//false
32
33 var obj6;
34 console.log(!!obj6);//false
35
36 var obj7=‘‘;
37 console.log(!!obj7);//false
38
39 var obj8=‘ ‘;
40 console.log(!!obj8);//true
41
42 var obj9=undefined;
43 console.log(!!obj9);//false
44
45 var obj10=null;
46 console.log(!!obj10);//false
47 }
48 function isSupportHistoryPushState(){
49 console.log(!!(window.history && history.pushState));//
50 return !!(window.history && history.pushState);//返回true or false
51 }
52 </script>
53 </head>
54 <body>
55 <input type="button" onclick="test();" value="test!!的使用方式"/>
56 <input type="button" onclick="isSupportHistoryPushState();" value="判断浏览器是否支持history.pushState"/>
57 </body>
58 </html>
时间： 2024-10-19 21:48:48