JS 规范及实现（V8）

5月 302013

缘起

JS的escape到底是怎么实现的？如：

escape(String.fromCharCode(0x41))
"A"
escape(String.fromCharCode(129))
"%81"
escape(String.fromCharCode(257))
"%u0101"

escape(String.fromCharCode(0x41))

"A"

escape(String.fromCharCode(129))

"%81"

escape(String.fromCharCode(257))

"%u0101"

哪些字符不做编码？哪些字符做 ‘%’ 编码？哪些字符做 ‘%u’ 编码？

参考资料：

Ecma： http://www.ecma-international.org/publications/standards/Ecma-262.htm

1. Call ToString(string).
2. Compute the number of characters in Result(1).
3. Let R be the empty string.
4. Let k be 0.
5. If k equals Result(2), return R.
6. Get the character (represented as a 16-bit unsigned integer) at position k within Result(1).
7. If Result(6) is one of the 69 nonblank characters
“ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789@*_+-./”
then go to step 13.
8. If Result(6), is less than 256, go to step 11.
9. Let S be a String containing six characters “%uwxyz” where wxyz are four hexadecimal digits encoding the 
value of Result(6).
10. Go to step 14.
11. Let S be a String containing three characters “%xy” where xy are two hexadecimal digits encoding the value 
of Result(6).
12. Go to step 14.
13. Let S be a String containing the single character Result(6).
14. Let R be a new String value computed by concatenating the previous value of R and S.
15. Increase k by 1.
16. Go to step 5.

1. Call ToString(string).

2. Compute the number of characters in Result(1).

3. Let R be the empty string.

4. Let k be 0.

5. If k equals Result(2), return R.

6. Get the character (represented as a 16-bit unsigned integer) at position k within Result(1).

7. If Result(6) is one of the 69 nonblank characters

“ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789@*_+-./”

then go to step 13.

8. If Result(6), is less than 256, go to step 11.

9. Let S be a String containing six characters “%uwxyz” where wxyz are four hexadecimal digits encoding the

value of Result(6).

10. Go to step 14.

11. Let S be a String containing three characters “%xy” where xy are two hexadecimal digits encoding the value

of Result(6).

12. Go to step 14.

13. Let S be a String containing the single character Result(6).

14. Let R be a new String value computed by concatenating the previous value of R and S.

15. Increase k by 1.

16. Go to step 5.

Google V8项目主页： https://code.google.com/p/v8/

Google V8源码下载： https://code.google.com/p/v8/wiki/Source 参看：uri.h中 URIEscape::Escape 的实现

Google V8开发者参考： https://developers.google.com/v8/build

关于JS做压缩：

http://www.poluoluo.com/jzxy/201004/83108.html

lz77

JS二进制操作： http://blog.chinaunix.net/uid-52437-id-3325514.html

原文链接：https://phpor.net/blog/post/1893

PHPor 的Blog

JS 规范及实现（V8）

缘起

参考资料：

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