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67、立即执行函数 <!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 // let num = 20 // (function(){ // console.log(11) // })() // (function(){ // let num = 10 // })(); // (function(){ // let num = 20 // })(); // 1、第一种写法 (function(x, y){ console.log(x + y) })(1, 2); // (function(){})(); // 2、第二种写法 (function(){}()); (function(x, y){ console.log(x + y) }(1, 3)); </script> </body> </html> -
66、函数表达式 <!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> // 3 + 4 // num = 10 // 1、函数表达式 let fn = function(x, y){ // console.log('我是函数表达式') console.log(x + y) } fn(1, 2) // 函数表达式和 具名函数的不同 function fn () // 1、具名函数的调用可以写在任何位置 // 2、函数表达式，必须先写表达式，后调用 function fun(){ console.log(1) } fun() </script> </body> </html>
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65、变量的特殊情况 <!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 = 20 function fn(){ num = 10 //全局变量来看 //强烈不允许 } fn() console.log(num) function fun(x, y){ console.log(x) } fun(1, 2) console.log(x) //错误 </script> </body> </html>
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64、作用域 <!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 console.log(num) //全局变量 function fn(){ console.log(num) } fn() // 2、局部变量 //函数变量 function fun(){ let str = 'pink' console.log(str) } fun() // 写外面会错误 </script> </body> </html>
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63、函数细节 <!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> function getSum(x, y){ return x + y // 返回值返回给了谁？函数的调用者 getSum(1, 2) } let num = parseInt('12px') let result = getSum(1, 2) console.log(result) </script> </body> </html>
