<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>第一种场景</title> <script type="text/javascript"> ----------------------------------------------------------------- var a = 1; function fn1(){ alert(a); //1 } fn1(); var a = 1; function fn1(){ alert(a); //undefined if (false) { var a = 3; }; } fn1(); ------------------------------------------------------------------- var a = 1; function fn1(){ alert(a); //undefined if (false) { //函数执行的时候，即使这部分代码没有执行，会创建局部的var time=未定义，所以未定义，函数体中没有通过var声明的变量，会加入到全局window作用域中 var a = 2; function fun() {//函数要执行才加入局部作用域 console.log("I am inside!"); }; }; fun();//fun is not a function,变为true就是I am inside! } fn1(); ------------------------------------------------------------------- var a = 1; function fn1(){ alert(a); //undefined if (true) { var a = 2; function fun() {//函数要执行才加入局部作用域 console.log("I am inside!"); }; }; fun();//I am inside! } fn1(); </script> </head> <body> </body> </html>
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>第一种场景</title> <script type="text/javascript"> var string = "Hello World!"; for (var i = 0; i < string.length; i++) { console.log(string[i]);//H e l l o W o r l d ! }; console.log("循环结束"); console.log(i); //12 </script> </head> <body> </body> </html>
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>块级作用域</title> <script src="../../../vendor/traceur.js"></script> <script src="../../../vendor/bootstrap.js"></script> <script type="text/javascript"> console.log("ES5:"); function fun() { var num = 100; if (true) { var num = 200; }; console.log(num); }; fun(); //200 </script> <script type="text/traceur"> console.log("ES6:"); function fun() { let num = 100; if (true) { let num = 200; console.log(num);//200 }; console.log(num);//100 }; fun(); //100 </script> </head> <body> </body> </html>
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>立即执行函数</title> <script src="../../../vendor/traceur.js"></script> <script src="../../../vendor/bootstrap.js"></script> <script type="text/javascript"> console.log("ES5:"); function fun() { console.log("I am outside!"); }; (function () { function fun() { console.log("I am inside!"); }; fun();//I am inside! }()); fun();//I am outside! (function () { if (false) {//函数不加入局部作用域 function fun() { console.log("I am inside!"); }; }; fun();// fun is not a function }()); fun();//I am outside! (function () { if (true) {//加入局部作用域 function fun() { console.log("I am inside!"); }; }; fun();// I am inside! }()); fun();//I am outside! </script> <script type="text/traceur"> console.log("ES6:"); function fun() { console.log("I am outside!"); }; (function () { if (false) { function fun() {//只在大括号范围内有效。es6块级作用域 console.log("I am inside!"); }; }; fun();//I am outside! }()); fun();//I am outside! </script> </head> <body> </body> </html>