From 750f3a32bf04a5dd953e2c9d75ef916b4ac69bc2 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E8=B0=A2=E9=87=91=E9=87=91?= <1665966989@qq.com> Date: Wed, 2 Nov 2022 00:00:27 +0000 Subject: [PATCH] 26 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Signed-off-by: 谢金金 <1665966989@qq.com> --- ...55\345\214\205\347\254\224\350\256\260.md" | 65 +++++++++++++++++++ 1 file changed, 65 insertions(+) create mode 100644 "26\350\260\242\351\207\221\351\207\221/\347\254\224\350\256\260/10.31\351\227\255\345\214\205\347\254\224\350\256\260.md" diff --git "a/26\350\260\242\351\207\221\351\207\221/\347\254\224\350\256\260/10.31\351\227\255\345\214\205\347\254\224\350\256\260.md" "b/26\350\260\242\351\207\221\351\207\221/\347\254\224\350\256\260/10.31\351\227\255\345\214\205\347\254\224\350\256\260.md" new file mode 100644 index 0000000..82bafd9 --- /dev/null +++ "b/26\350\260\242\351\207\221\351\207\221/\347\254\224\350\256\260/10.31\351\227\255\345\214\205\347\254\224\350\256\260.md" @@ -0,0 +1,65 @@ +| 一、变量的作用域： | | | +| ------------------ | ------------------------------------------------------------ | ------------------------------------------------------------ | +| | [2](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_2) | | +| | [3](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_3) | 函数内部可以直接读取全局变量。 | +| | [4](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_4) | | +| | [5](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_5) | var n=999; | +| | [6](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_6) | | +| | [7](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_7) | function f1(){ | +| | [8](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_8) | alert(n); | +| | [9](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_9) | } | +| | [10](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_10) | | +| | [11](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_11) | f1(); // 999 | +| | [12](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_12) | | +| | [13](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_13) | 在函数外部无法读取函数内的局部变量 | +| | [14](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_14) | | +| | [15](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_15) | function f1(){ | +| | [16](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_16) | var n=999; | +| | [17](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_17) | } | +| | [18](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_18) | | +| | [19](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_19) | alert(n); // error | +| | [20](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_20) | | +| | [21](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_21) | 这里有一个地方需要注意， 函数内部声明变量的时候，一定要使用var命令。如果不用的话，你实际上声明了一个全局变量！ | +| | [22](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_22) | | +| | [23](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_23) | function f1(){ | +| | [24](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_24) | n=999; | +| | [25](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_25) | | +| | [26](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_26) | } | +| | [27](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_27) | | +| | [28](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_28) | f1(); | +| | [29](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_29) | | +| | [30](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_30) | alert(n); // 999 | +| | [31](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_31) | | +| | [32](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_32) | 二、如何从外部读取局部变量 | +| | [33](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_33) | | +| | [34](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_34) | 只有通过变通方法才能实现从外部读取局部变量。那就是在函数的内部，再定义一个函数。 | +| | [35](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_35) | | +| | [36](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_36) | function f1(){ | +| | [37](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_37) | | +| | [38](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_38) | var n=999; | +| | [39](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_39) | | +| | [40](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_40) | function f2(){ | +| | [41](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_41) | alert(n); // 999 | +| | [42](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_42) | } | +| | [43](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_43) | | +| | [44](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_44) | } | +| | [45](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_45) | | +| | [46](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_46) | 在上面的代码中，函数f2就被包括在函数f1内部，这时f1内部的所有局部变量，对f2都是可见的。但是反过来就不行，f2内部的局部变量，对f1就是不可见的。父对象的所有变量，对子对象都是可见的，反之则不成立。 | +| | [47](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_47) | | +| | [48](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_48) | 既然f2可以读取f1中的局部变量，那么只要把f2作为返回值，我们不就可以在f1外部读取它的内部变量了吗！ | +| | [49](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_49) | | +| | [50](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_50) | function f1(){ | +| | [51](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_51) | | +| | [52](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_52) | var n=999; | +| | [53](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_53) | | +| | [54](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_54) | function f2(){ | +| | [55](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_55) | alert(n); | +| | [56](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_56) | } | +| | [57](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_57) | | +| | [58](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_58) | return f2; | +| | [59](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_59) | | +| | [60](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_60) | } | +| | [61](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_61) | | +| | [62](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_62) | var result=f1(); | +| | [63](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_63) | | +| | [64](https://gitee.com/level-21-software-class-4/java-script/pulls/204/files#9e66d4810c780fb9ffb863aa94af2a3420412470_0_64) | result(); // 999 | \ No newline at end of file -- Gitee