作者：柯云，来自原文地址 
背景：使用微信小程序调用https接口，md5加密当前时间戳，然后再md5(时间戳的md5+约定好的key)生成token，来实现简单校验。服务端接口，判断时间戳是否在有效时间内，然后生成token对比传过来的token。

微信小程序使用的开发语言是js，网上找到js实现md5加密的代码，融合进小程序内使用

在utils目录下新建md5.js文件

1. function safeAdd (x, y) {
2. var lsw = (x & 0xFFFF) + (y & 0xFFFF)
3. var msw = (x >> 16) + (y >> 16) + (lsw >> 16)
4. return (msw << 16) | (lsw & 0xFFFF)
5. }
6.  
7. /*
8. * Bitwise rotate a 32-bit number to the left.
9. */
10. function bitRotateLeft (num, cnt) {
11. return (num << cnt) | (num >>> (32 - cnt))
12. }
13.  
14. /*
15. * These functions implement the four basic operations the algorithm uses.
16. */
17. function md5cmn (q, a, b, x, s, t) {
18. return safeAdd(bitRotateLeft(safeAdd(safeAdd(a, q), safeAdd(x, t)), s), b)
19. }
20. function md5ff (a, b, c, d, x, s, t) {
21. return md5cmn((b & c) | ((~b) & d), a, b, x, s, t)
22. }
23. function md5gg (a, b, c, d, x, s, t) {
24. return md5cmn((b & d) | (c & (~d)), a, b, x, s, t)
25. }
26. function md5hh (a, b, c, d, x, s, t) {
27. return md5cmn(b ^ c ^ d, a, b, x, s, t)
28. }
29. function md5ii (a, b, c, d, x, s, t) {
30. return md5cmn(c ^ (b | (~d)), a, b, x, s, t)
31. }
32.  
33. /*
34. * Calculate the MD5 of an array of little-endian words, and a bit length.
35. */
36. function binlMD5 (x, len) {
37. /* append padding */
38. x[len >> 5] |= 0x80 << (len % 32)
39. x[(((len + 64) >>> 9) << 4) + 14] = len
40.  
41. var i
42. var olda
43. var oldb
44. var oldc
45. var oldd
46. var a = 1732584193
47. var b = -271733879
48. var c = -1732584194
49. var d = 271733878
50.  
51. for (i = 0; i < x.length; i += 16) {
52. olda = a
53. oldb = b
54. oldc = c
55. oldd = d
56.  
57. a = md5ff(a, b, c, d, x[i], 7, -680876936)
58. d = md5ff(d, a, b, c, x[i + 1], 12, -389564586)
59. c = md5ff(c, d, a, b, x[i + 2], 17, 606105819)
60. b = md5ff(b, c, d, a, x[i + 3], 22, -1044525330)
61. a = md5ff(a,