<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> </head> <body> <script> var y=19; var z=x-y; console.log(z); var x=1; // x++ increment, same as x=x+1; console.log(x); var x=1; ++x; console.log(x); // x++ is the same as ++. Var x=1; // console.log(x++); Var x="hello"; var x="hello"; var y="world"; var z=x+y; console.log(z); Var x=1; var x=1; var y="hello"; var z=x+y; console.log(z); // If you add a number to a string, the value is converted to a string by default. var y=20; var z=x==y; console.log(z); Var x=20; var x=20; var y=30; // x+y =y; console.log(x); / / / / the logical operators and && and | | not! var x=20; var y=x>10&&x<30; console.log(y) </script> </body> </html>Copy the code