1 <script>
2 "use strict";
3 var data1 = 0,
4 data2 = "",
5 data3 = false,
6 data4 = undefined,
7 data5 = null;
8 // 下面全部为false
9 console.log(!!data1);
10 console.log(Boolean(data1));
11 console.log(Boolean(data2));
12 console.log(Boolean(data3));
13 console.log(Boolean(data4));
14 console.log(Boolean(data5));
15 </script>
16
17 <script>
18 "use strict";
19
20 var num= "8000";
21 console.log(num); // "8000"
22 console.log(+num); // 8000
23 console.log(-num); // -8000
24 console.log(num - 100); // 7900
25 console.log(num + 100); // 8000100
26 </script>
