获取openid和session_key
https://developers.weixin.qq.com/miniprogram/dev/api/api-login.html

工具md5加密

/* * A JavaScript implementation of the RSA Data Security, Inc. MD5 Message * Digest Algorithm, as defined in RFC 1321. * Version 1.1 Copyright (C) Paul Johnston 1999 - 2002. * Code also contributed by Greg Holt * See http://pajhome.org.uk/site/legal.html for details. *//* * Add integers, wrapping at 2^32. This uses 16-bit operations internally * to work around bugs in some JS interpreters. */
function safe_add(x, y) {var lsw = (x & 0xFFFF) + (y & 0xFFFF)var msw = (x >> 16) + (y >> 16) + (lsw >> 16)return (msw << 16) | (lsw & 0xFFFF)
}/* * Bitwise rotate a 32-bit number to the left. */
function rol(num, cnt) {return (num << cnt) | (num >>> (32 - cnt))
}/* * These functions implement the four basic operations the algorithm uses. */
function cmn(q, a, b, x, s, t) {return safe_add(rol(safe_add(safe_add(a, q), safe_add(x, t)), s), b)
}
function ff(a, b, c, d, x, s, t) {return cmn((b & c) | ((~b) & d), a, b, x, s, t)
}
function gg(a, b, c, d, x, s, t) {return cmn((b & d) | (c & (~d)), a, b, x, s, t)
}
function hh(a, b, c, d, x, s, t) {return cmn(b ^ c ^ d, a, b, x, s, t)
}
function ii(a, b, c, d, x, s, t) {return cmn(c ^ (b | (~d)), a, b, x, s, t)
}/* * Calculate the MD5 of an array of little-endian words, producing an array * of little-endian words. */
function coreMD5(x) {var a = 1732584193var b = -271733879var c = -1732584194var d = 271733878for (var i = 0; i < x.length; i += 16) {var olda = avar oldb = bvar oldc = cvar oldd = da = ff(a, b, c, d, x[i + 0], 7, -680876936)d = ff(d, a, b, c, x[i + 1], 12, -389564586)c = ff(c, d, a, b, x[i + 2], 17, 606105819)b = ff(b, c, d, a, x[i + 3], 22, -1044525330)a = ff(a, b, c, d, x[i + 4], 7, -176418897)d = ff(d, a, b, c, x[i + 5], 12, 1200080426)c = ff(c, d, a, b, x[i + 6], 17, -1473231341)b = ff(b, c, d, a, x[i + 7], 22, -45705983)a = ff(a, b, c, d, x[i + 8], 7, 1770035416)d = ff(d, a, b, c, x[i + 9], 12, -1958414417)c = ff(c, d, a, b, x[i + 10], 17, -42063)b = ff(b, c, d, a, x[i + 11], 22, -1990404162)a = ff(a, b, c, d, x[i + 12], 7, 1804603682)d = ff(d, a, b, c, x[i + 13], 12, -40341101)c = ff(c, d, a, b, x[i + 14], 17, -1502002290)b = ff(b, c, d, a, x[i + 15], 22, 1236535329)a = gg(a, b, c, d, x[i + 1], 5, -165796510)d = gg(d, a, b, c, x[i + 6], 9, -1069501632)c = gg(c, d, a, b, x[i + 11], 14, 643717713)b = gg(b, c, d, a, x[i + 0], 20, -373897302)a = gg(a, b, c, d, x[i + 5], 5, -701558691)d = gg(d, a, b, c, x[i + 10], 9, 38016083)c = gg(c, d, a, b, x[i + 15], 14, -660478335)b = gg(b, c, d, a, x[i + 4], 20, -405537848)a = gg(a, b, c, d, x[i + 9], 5, 568446438)d = gg(d, a, b, c, x[i + 14], 9, -1019803690)c = gg(c, d, a, b, x[i + 3], 14, -187363961)b = gg(b, c, d, a, x[i + 8], 20, 1163531501)a = gg(a, b, c, d, x[i + 13], 5, -1444681467)d = gg(d, a, b, c, x[i + 2], 9, -51403784)c = gg(c, d, a, b, x[i + 7], 14, 1735328473)b = gg(b, c, d, a, x[i + 12], 20, -1926607734)a = hh(a, b, c, d, x[i + 5], 4, -378558)d = hh(d, a, b, c, x[i + 8], 11, -2022574463)c = hh(c, d, a, b, x[i + 11], 16, 1839030562)b = hh(b, c, d, a, x[i + 14], 23, -35309556)a = hh(a, b, c, d, x[i + 1], 4, -1530992060)d = hh(d, a, b, c, x[i + 4], 11, 1272893353)c = hh(c, d, a, b, x[i + 7], 16, -155497632)b = hh(b, c, d, a, x[i + 10], 23, -1094730640)a = hh(a, b, c, d, x[i + 13], 4, 681279174)d = hh(d, a, b, c, x[i + 0], 11, -358537222)c = hh(c, d, a, b, x[i + 3], 16, -722521979)b = hh(b, c, d, a, x[i + 6], 23, 76029189)a = hh(a, b, c, d, x[i + 9], 4, -640364487)d = hh(d, a, b, c, x[i + 12], 11, -421815835)c = hh(c, d, a, b, x[i + 15], 16, 530742520)b = hh(b, c, d, a, x[i + 2], 23, -995338651)a = ii(a, b, c, d, x[i + 0], 6, -198630844)d = ii(d, a, b, c, x[i + 7], 10, 1126891415)c = ii(c, d, a, b, x[i + 14], 15, -1416354905)b = ii(b, c, d, a, x[i + 5], 21, -57434055)a = ii(a, b, c, d, x[i + 12], 6, 1700485571)d = ii(d, a, b, c, x[i + 3], 10, -1894986606)c = ii(c, d, a, b, x[i + 10], 15, -1051523)b = ii(b, c, d, a, x[i + 1], 21, -2054922799)a = ii(a, b, c, d, x[i + 8], 6, 1873313359)d = ii(d, a, b, c, x[i + 15], 10, -30611744)c = ii(c, d, a, b, x[i + 6], 15, -1560198380)b = ii(b, c, d, a, x[i + 13], 21, 1309151649)a = ii(a, b, c, d, x[i + 4], 6, -145523070)d = ii(d, a, b, c, x[i + 11], 10, -1120210379)c = ii(c, d, a, b, x[i + 2], 15, 718787259)b = ii(b, c, d, a, x[i + 9], 21, -343485551)a = safe_add(a, olda)b = safe_add(b, oldb)c = safe_add(c, oldc)d = safe_add(d, oldd)}return [a, b, c, d]
}/* * Convert an array of little-endian words to a hex string. */
function binl2hex(binarray) {var hex_tab = "0123456789abcdef"var str = ""for (var i = 0; i < binarray.length * 4; i++) {str += hex_tab.charAt((binarray[i >> 2] >> ((i % 4) * 8 + 4)) & 0xF) +hex_tab.charAt((binarray[i >> 2] >> ((i % 4) * 8)) & 0xF)}return str
}/* * Convert an array of little-endian words to a base64 encoded string. */
function binl2b64(binarray) {var tab = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"var str = ""for (var i = 0; i < binarray.length * 32; i += 6) {str += tab.charAt(((binarray[i >> 5] << (i % 32)) & 0x3F) |((binarray[i >> 5 + 1] >> (32 - i % 32)) & 0x3F))}return str
}/* * Convert an 8-bit character string to a sequence of 16-word blocks, stored * as an array, and append appropriate padding for MD4/5 calculation. * If any of the characters are >255, the high byte is silently ignored. */
function str2binl(str) {var nblk = ((str.length + 8) >> 6) + 1 // number of 16-word blocks  var blks = new Array(nblk * 16)for (var i = 0; i < nblk * 16; i++) blks[i] = 0for (var i = 0; i < str.length; i++)blks[i >> 2] |= (str.charCodeAt(i) & 0xFF) << ((i % 4) * 8)blks[i >> 2] |= 0x80 << ((i % 4) * 8)blks[nblk * 16 - 2] = str.length * 8return blks
}/* * Convert a wide-character string to a sequence of 16-word blocks, stored as * an array, and append appropriate padding for MD4/5 calculation. */
function strw2binl(str) {var nblk = ((str.length + 4) >> 5) + 1 // number of 16-word blocks  var blks = new Array(nblk * 16)for (var i = 0; i < nblk * 16; i++) blks[i] = 0for (var i = 0; i < str.length; i++)blks[i >> 1] |= str.charCodeAt(i) << ((i % 2) * 16)blks[i >> 1] |= 0x80 << ((i % 2) * 16)blks[nblk * 16 - 2] = str.length * 16return blks
}/* * External interface */
function hexMD5(str) { return binl2hex(coreMD5(str2binl(str))) }
function hexMD5w(str) { return binl2hex(coreMD5(strw2binl(str))) }
function b64MD5(str) { return binl2b64(coreMD5(str2binl(str))) }
function b64MD5w(str) { return binl2b64(coreMD5(strw2binl(str))) }
/* Backward compatibility */
function calcMD5(str) { return binl2hex(coreMD5(str2binl(str))) }
module.exports = {hexMD5: hexMD5
}

使用方法：

var utilMd5 = require('../../utils/md5.js');
var password = utilMd5.hexMD5("password");

小程序设置背景图的时候不能使用本地资源，必须使用在线资源或则是base64图片
base64转化：
http://imgbase64.duoshitong.com/
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在线设计
https://www.chuangkit.com
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在使用canvasToTempFilePath和saveimagetoalbum之后，保存下来的图片是在电脑端是看不到的，白色的，需要在手机才能看到，大坑啊！！！
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转发功能

需要给button 元素加上 open-type="share"，就可以了，不过一定要定义Page.onShareAppMessage() 事件,
https://developers.weixin.qq.com/miniprogram/dev/framework/app-service/page.html

设置倒计时的时候，使用setInterval函数，不能在页面生命周期里面去调用
要自己写方法在里面调用
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小程序微信样式库
https://github.com/Tencent/weui-wxss/tree/master/src/example
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