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207
篇与
的结果
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24、用户输入案例 <!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> </head> <body> <script> // 能被4整除，不能被100整除 // 1.用户输入 let num = prompt('请输入数字：') // 2.弹出结果 alert(num % 4 === 0 && num % 100 !== 0) </script> </body> </html> -
23、逻辑运算符 <!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> </head> <body> <script> // 逻辑与 一假则假 console.log(true && true) console.log(false && true) console.log(2 < 3 && 4 > 3) console.log(1 < 2 && 3 > 4) console.log('---------------') // 逻辑或 一真则真 console.log(true || true) console.log(false || true) console.log(false || false) console.log('--------------') // 逻辑非 取反 console.log(!true)//false console.log(!false)//true </script> </body> </html>
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22、比较运算符 <!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> </head> <body> <script> console.log(3 > 5) console.log(3 >= 3) console.log(2 == 2) // 比较运算符有隐式转换 把字符型的‘2’转换成数字类型的‘2’ 双等号只判断值 console.log(2 == '2') console.log(undefined == null)//true console.log(undefined === null)//false // 还判断数据类型 // 常用三等 === console.log(2 === '2') console.log(NaN === NaN) //NaN不等于任何人，包括他自己 console.log(2 !== '2')//true console.log(2 != '2')//false console.log('-------------------') console.log('a' < 'b')//true console.log('aa' < 'ab')//true </script> </body> </html>
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21、一元运算符 <!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> </head> <body> <script> // let num = 10 // num = num + 1 // num += 1 // 1.前置自增 // let i = 1 // ++i // console.log(i) // 1.后缀自增 // let i = 1 // i++ // console.log(i) let i = 1 console.log(i++ + ++i + i) </script> </body> </html>
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20、赋值运算符 <!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> </head> <body> <script> let num = 1 // num = num + 1 // 采取赋值运算法 num += 3 console.log(num) </script> </body> </html>
