ejs项目大名鼎鼎，应该就不需要介绍了，主要收获就是得知了实现一个模板引擎的流程，ejs是将模板作为字符串逐个解析，遇到正常的html代码，就放进一个数组中去，遇到js代码则进行过滤器、包含等的处理，最后数组join成一个可以成为Function构造函数第二个参数的字符串，构造成构造函数之后就是调用返回最终的html字符串。以下是阅读源码的笔记，因为源码中遗憾有很多说明，所以笔记很少。
ejs = (function(){
// CommonJS require()
function require(p){
if ('fs' == p) return {};
if ('path' == p) return {};
var path = require.resolve(p)
, mod = require.modules[path];
if (!mod) throw new Error('failed to require "' + p + '"');
if (!mod.exports) {
mod.exports = {};
mod.call(mod.exports, mod, mod.exports, require.relative(path));
}
return mod.exports;
}
require.modules = {};
require.resolve = function (path){
var orig = path
, reg = path + '.js'
, index = path + '/index.js';
return require.modules[reg] && reg
|| require.modules[index] && index
|| orig;
};
require.register = function (path, fn){
require.modules[path] = fn;
};
require.relative = function (parent) {
return function(p){
if ('.' != p.substr(0, 1)) return require(p);
var path = parent.split('/')
, segs = p.split('/');
path.pop();
for (var i = 0; i < segs.length; i++) {
var seg = segs[i];
if ('..' == seg) path.pop();
else if ('.' != seg) path.push(seg);
}
return require(path.join('/'));
};
};
require.register("ejs.js", function(module, exports, require){
/*!
* EJS
* Copyright(c) 2012 TJ Holowaychuk <tj@vision-media.ca>
* MIT Licensed
*/
/**
* Module dependencies.
*/
var utils = require('./utils')
, path = require('path')
, dirname = path.dirname
, extname = path.extname
, join = path.join
, fs = require('fs')
, read = fs.readFileSync;
/**
* Filters.
*
* @type Object
*/
var filters = exports.filters = require('./filters');
/**
* Intermediate js cache.
*
* @type Object
*/
var cache = {};
/**
* Clear intermediate js cache.
*
* @api public
*/
exports.clearCache = function(){
cache = {};
};
/**
* Translate filtered code into function calls.
*
* @param {String} js
* @return {String}
* @api private
*/
function filtered(js) {
return js.substr(1).split('|').reduce(function(js, filter){
var parts = filter.split(':')
, name = parts.shift()
, args = parts.join(':') || '';
if (args) args = ', ' + args;
return 'filters.' + name + '(' + js + args + ')';
});
};
/**
* Re-throw the given `err` in context to the
* `str` of ejs, `filename`, and `lineno`.
*
* @param {Error} err
* @param {String} str
* @param {String} filename
* @param {String} lineno
* @api private
*/
function rethrow(err, str, filename, lineno){
var lines = str.split('\n')
, start = Math.max(lineno - 3, 0)
, end = Math.min(lines.length, lineno + 3);
// Error context
var context = lines.slice(start, end).map(function(line, i){
var curr = i + start + 1;
return (curr == lineno ? ' >> ' : ' ')
+ curr
+ '| '
+ line;
}).join('\n');
// Alter exception message
err.path = filename;
err.message = (filename || 'ejs') + ':'
+ lineno + '\n'
+ context + '\n\n'
+ err.message;
throw err;
}
/**
* Parse the given `str` of ejs, returning the function body.
*
* @param {String} str
* @return {String}
* @api public
*/
var parse = exports.parse = function(str, options){
var options = options || {}
, open = options.open || exports.open || '<%'
, close = options.close || exports.close || '%>'
, filename = options.filename
, compileDebug = options.compileDebug !== false
, buf = "";
buf += 'var buf = [];';
if (false !== options._with) buf += '\nwith (locals || {}) { (function(){ ';
buf += '\n buf.push(\'';
var lineno = 1;
var consumeEOL = false;
for (var i = 0, len = str.length; i < len; ++i) {
var stri = str[i];
if (str.slice(i, open.length + i) == open) {
i += open.length
var prefix, postfix, line = (compileDebug ? '__stack.lineno=' : '') + lineno;
switch (str[i]) {
case '=':
prefix = "', escape((" + line + ', ';
postfix = ")), '";
++i;
break;
case '-':
prefix = "', (" + line + ', ';
postfix = "), '";
++i;
break;
default:
prefix = "');" + line + ';';
postfix = "; buf.push('";
}
// 查找对应的结尾
var end = str.indexOf(close, i);
if (end < 0){
throw new Error('Could not find matching close tag "' + close + '".');
}
// 提取模板中的js代码
var js = str.substring(i, end)
, start = i
, include = null
, n = 0;
// 结尾-表示不需要转义，这种情况<%- code -%>
if ('-' == js[js.length-1]){
js = js.substring(0, js.length - 2);
consumeEOL = true;
}
// 处理调用include情况 <%- include() %>
if (0 == js.trim().indexOf('include')) {
var name = js.trim().slice(7).trim();
if (!filename) throw new Error('filename option is required for includes');
var path = resolveInclude(name, filename);
include = read(path, 'utf8');
include = exports.parse(include, { filename: path, _with: false, open: open, close: close, compileDebug: compileDebug });
buf += "' + (function(){" + include + "})() + '";
js = '';
}
// 处理js代码换行的情况，又路遇装逼犯，~(n = js.indexOf("\n", n))就是存在换行符情况之下执行
while (~(n = js.indexOf("\n", n))) n++, lineno++;
// 过滤器处理，<%=: users | map:'name' | join %>
if (js.substr(0, 1) == ':') js = filtered(js);
if (js) {
if (js.lastIndexOf('//') > js.lastIndexOf('\n')) js += '\n';
buf += prefix;
buf += js;
buf += postfix;
}
i += end - start + close.length - 1;
} else if (stri == "\\") {
buf += "\\\\";
} else if (stri == "'") {
buf += "\\'";
} else if (stri == "\r") {
// ignore
} else if (stri == "\n") {
if (consumeEOL) {
consumeEOL = false;
} else {
buf += "\\n";
lineno++;
}
} else {
buf += stri;
}
}
if (false !== options._with) buf += "'); })();\n} \nreturn buf.join('');";
else buf += "');\nreturn buf.join('');";
return buf;
};
/**
* Compile the given `str` of ejs into a `Function`.
*
* @param {String} str
* @param {Object} options
* @return {Function}
* @api public
*/
var compile = exports.compile = function(str, options){
options = options || {};
var escape = options.escape || utils.escape;
var input = JSON.stringify(str)
, compileDebug = options.compileDebug !== false
, client = options.client
, filename = options.filename
? JSON.stringify(options.filename)
: 'undefined';
if (compileDebug) {
// Adds the fancy stack trace meta info
str = [
'var __stack = { lineno: 1, input: ' + input + ', filename: ' + filename + ' };',
rethrow.toString(),
'try {',
exports.parse(str, options),
'} catch (err) {',
' rethrow(err, __stack.input, __stack.filename, __stack.lineno);',
'}'
].join("\n");
} else {
str = exports.parse(str, options);
}
if (options.debug) console.log(str);
if (client) str = 'escape = escape || ' + escape.toString() + ';\n' + str;
try {
// 别忘了，可以使用构造函数定义函数呀
var fn = new Function('locals, filters, escape, rethrow', str);
} catch (err) {
if ('SyntaxError' == err.name) {
err.message += options.filename
? ' in ' + filename
: ' while compiling ejs';
}
throw err;
}
if (client) return fn;
return function(locals){
return fn.call(this, locals, filters, escape, rethrow);
}
};
/**
* Render the given `str` of ejs.
*
* Options:
*
* - `locals` Local variables object
* - `cache` Compiled functions are cached, requires `filename`
* - `filename` Used by `cache` to key caches
* - `scope` Function execution context
* - `debug` Output generated function body
* - `open` Open tag, defaulting to "<%"
* - `close` Closing tag, defaulting to "%>"
*
* @param {String} str
* @param {Object} options
* @return {String}
* @api public
*/
// 渲染函数
exports.render = function(str, options){
var fn
, options = options || {};
// 检查是否缓存
if (options.cache) {
if (options.filename) {
fn = cache[options.filename] || (cache[options.filename] = compile(str, options));
} else {
throw new Error('"cache" option requires "filename".');
}
} else {
fn = compile(str, options);
}
options.__proto__ = options.locals;
return fn.call(options.scope, options);
};
/**
* Render an EJS file at the given `path` and callback `fn(err, str)`.
*
* @param {String} path
* @param {Object|Function} options or callback
* @param {Function} fn
* @api public
*/
exports.renderFile = function(path, options, fn){
var key = path + ':string';
if ('function' == typeof options) {
fn = options, options = {};
}
options.filename = path;
var str;
try {
str = options.cache
? cache[key] || (cache[key] = read(path, 'utf8'))
: read(path, 'utf8');
} catch (err) {
fn(err);
return;
}
fn(null, exports.render(str, options));
};
/**
* Resolve include `name` relative to `filename`.
*
* @param {String} name
* @param {String} filename
* @return {String}
* @api private
*/
function resolveInclude(name, filename) {
var path = join(dirname(filename), name);
var ext = extname(name);
if (!ext) path += '.ejs';
return path;
}
// express support
exports.__express = exports.renderFile;
/**
* Expose to require().
*/
if (require.extensions) {
require.extensions['.ejs'] = function (module, filename) {
filename = filename || module.filename;
var options = { filename: filename, client: true }
, template = fs.readFileSync(filename).toString()
, fn = compile(template, options);
module._compile('module.exports = ' + fn.toString() + ';', filename);
};
} else if (require.registerExtension) {
require.registerExtension('.ejs', function(src) {
return compile(src, {});
});
}
}); // module: ejs.js
require.register("filters.js", function(module, exports, require){
/*!
* EJS - Filters
* Copyright(c) 2010 TJ Holowaychuk <tj@vision-media.ca>
* MIT Licensed
*/
/**
* First element of the target `obj`.
*/
// 过滤函数
exports.first = function(obj) {
return obj[0];
};
/**
* Last element of the target `obj`.
*/
// 过滤函数
exports.last = function(obj) {
return obj[obj.length - 1];
};
/**
* Capitalize the first letter of the target `str`.
*/
// 过滤函数
exports.capitalize = function(str){
str = String(str);
return str[0].toUpperCase() + str.substr(1, str.length);
};
/**
* Downcase the target `str`.
*/
// 过滤函数
exports.downcase = function(str){
return String(str).toLowerCase();
};
/**
* Uppercase the target `str`.
*/
// 过滤函数
exports.upcase = function(str){
return String(str).toUpperCase();
};
/**
* Sort the target `obj`.
*/
// 过滤函数
exports.sort = function(obj){
return Object.create(obj).sort();
};
/**
* Sort the target `obj` by the given `prop` ascending.
*/
exports.sort_by = function(obj, prop){
return Object.create(obj).sort(function(a, b){
a = a[prop], b = b[prop];
if (a > b) return 1;
if (a < b) return -1;
return 0;
});
};
/**
* Size or length of the target `obj`.
*/
exports.size = exports.length = function(obj) {
return obj.length;
};
/**
* Add `a` and `b`.
*/
exports.plus = function(a, b){
return Number(a) + Number(b);
};
/**
* Subtract `b` from `a`.
*/
exports.minus = function(a, b){
return Number(a) - Number(b);
};
/**
* Multiply `a` by `b`.
*/
exports.times = function(a, b){
return Number(a) * Number(b);
};
/**
* Divide `a` by `b`.
*/
exports.divided_by = function(a, b){
return Number(a) / Number(b);
};
/**
* Join `obj` with the given `str`.
*/
exports.join = function(obj, str){
return obj.join(str || ', ');
};
/**
* Truncate `str` to `len`.
*/
exports.truncate = function(str, len, append){
str = String(str);
if (str.length > len) {
str = str.slice(0, len);
if (append) str += append;
}
return str;
};
/**
* Truncate `str` to `n` words.
*/
exports.truncate_words = function(str, n){
var str = String(str)
, words = str.split(/ +/);
return words.slice(0, n).join(' ');
};
/**
* Replace `pattern` with `substitution` in `str`.
*/
exports.replace = function(str, pattern, substitution){
return String(str).replace(pattern, substitution || '');
};
/**
* Prepend `val` to `obj`.
*/
exports.prepend = function(obj, val){
return Array.isArray(obj)
? [val].concat(obj)
: val + obj;
};
/**
* Append `val` to `obj`.
*/
exports.append = function(obj, val){
return Array.isArray(obj)
? obj.concat(val)
: obj + val;
};
/**
* Map the given `prop`.
*/
exports.map = function(arr, prop){
return arr.map(function(obj){
return obj[prop];
});
};
/**
* Reverse the given `obj`.
*/
exports.reverse = function(obj){
return Array.isArray(obj)
? obj.reverse()
: String(obj).split('').reverse().join('');
};
/**
* Get `prop` of the given `obj`.
*/
exports.get = function(obj, prop){
return obj[prop];
};
/**
* Packs the given `obj` into json string
*/
exports.json = function(obj){
return JSON.stringify(obj);
};
}); // module: filters.js
require.register("utils.js", function(module, exports, require){
/*!
* EJS
* Copyright(c) 2010 TJ Holowaychuk <tj@vision-media.ca>
* MIT Licensed
*/
/**
* Escape the given string of `html`.
*
* @param {String} html
* @return {String}
* @api private
*/
exports.escape = function(html){
return String(html)
.replace(/&/g, '&')
.replace(/</g, '<')
.replace(/>/g, '>')
.replace(/'/g, ''')
.replace(/"/g, '"');
};
}); // module: utils.js
return require("ejs");
})();
