Juicer - A fast template engine using javascript

一个前端 Javascript 模板引擎的实现与优化

流火 @ TaobaoUED
Blog: http://benben.cc

12年5月28日星期⼀一

Who am i ?
【诗经・国风・豳风】七月流火，九月授衣。

Blog: http://benben.cc
Github: http://github.com/PaulGuo
Weibo: http://weibo.com/janbing
Twitter: http://twitter.com/guokai

【一些开源项目】

【在哪】


doT yayaTemplate
ejs
Mustache
artTemplate
nTenjin handlebar
Kissy template
micro template

...
jQuery tmpl


is it nessary ? are u sure ?

如无必要，勿增实体


Juicer 的特点 support node.js only 5kb

1 循环 {@each}…{@/each}

2 判断 {@if}…{@else if}…{@else}…{@/if}

3 变量（支持自定义函数） ${varname|function}

4 注释 {# comment here}

5 辅助循环 {@each i in range(0,9)}

6 自定义函数，扩展灵活 register/unregister


模板引擎基本原理

模板引擎的基本机理就是替换（转换），将指定的标签转换为
需要的业务数据；将指定的伪语句按照某种流程来变换输出。

The gist of JavaScript templates is that you can take an HTML fragment interpolated
with template variables and combine it with a JavaScript object, replacing those
template variables with values from the object. Overall, JavaScript templating
works in much the same way as templating libraries in other languages, such as
PHP’s Smarty, Ruby’s ERB, and Python’s string formatting.

- Javascript Web Application


water juicer fruits

Template
JSON Engine
Template

HTML
Fragment


模板引擎的分类

·置换型模板引擎。

·解释型模板引擎。

·编译型模板引擎。


静态页面含有丰富交互的应用服务端
后端提供纯数据（接口化）
前端负责将数据生成页面


MVC 需要模板

MVC最早是在SmallTalk语言的开发过程中总结出的一种设
计模式，MVC分别代表了"模型"、"视图"和"控制"，目的就
是让不同的开发角色在大中型项目中各司其职。在网络应
用程序的开发中，可以用下图来表示各概念之间的关系。


现实中的使用场景


拼字符串

var json = { name: "liuhuo", blog: "ued.taobao.com"};

var html = '<span class="name">' + json.name + ' (blog: ' + json.blog + ')</span>';

<span class="name">流火 (blog: ued.taobao.com)</span>


YUI.Lang.sub

function sub(str,data) {
return str
.replace(/{(.*?)}/igm,function($,$1) {
return data[$1]?data[$1]:$;
});
}

var tpl = '<span class="name">{name} (blog: {blog})</span>';

var html = sub(tpl, json);


Security
XSS escape

Syntax Performance
easy to write & read as faster as you can

Error Handling
robustness


语法

主张原生语法的传统模板引擎主张Logic-less的新兴模板引擎

ejs、nTenjin、doT mustache、handlebars
{{#list}}
{{#a}} {{value}} {{/a}}

追求纯粹，希望通过原生的追求 KISS / Logic less, 这注定了这
Javascript 语法来写模板，这类模类模板引擎的实现是解释型的，
板引擎的实现一定是编译型的，也就注定了它们性能是有瓶颈
但是它们的写法往往让人抓狂。的。

jQuery Tmpl、kissy Template

the templating syntax for most libraries is very similar, if not identical. - Javascript Web Application


JSON HTML

var data={
<ul>
    list:[
    <li>liuhuo (index: 0)</li>
        {name:'liuhuo',show:true},
    <li>taobao (index: 2)</li>
        {name:'benben',show:false},
    <li>num: 1</li>
        {name:'taobao',show:true}
    <li>num: 2</li>
    ],
    <li>num: 3</li>
    blah:[
    <li>15:00</li>
        {num:1},
    <li>16:00</li>
        {num:2},
    <li>17:00</li>
        {num:3,inner:[
    <li>18:00</li>
            {'time':'15:00'},
    <li>num: 4</li>
            {'time':'16:00'},
</ul>
            {'time':'17:00'},
            {'time':'18:00'}
        ]},
        {num:4}
    ]
};


语法 | doT、nTenjin、ejs、tmpl

<ul>
  <?js for(var i=0;i<it.list.length;i++) { ?>
  <?js if(it.list[i].show) { ?>
  <li>${it.list[i].name} (index: ${i})</li>
  <?js } ?>
  <?js } ?>
  <?js for(var i=0;i<it.blah.length;i++) { ?>
  <li>
  num: ${it.blah[i].num}
  <?js if(it.blah[i].num==3) { ?>
  <?js for(var j=0;j<it.blah[i].inner.length;j++) { ?>
  <li>${it.blah[i].inner[j].time}</li>
  <?js } ?>
  <?js } ?>
  </li>
  <?js } ?>
</ul>


语法 | doT、nTenjin、ejs、tmpl

<ul>
  <% for(var i=0;i<list.length;i++) { %>
  <% if(list[i].show) { %>
  <li><%= list[i].name %> (index: <%= i %>)</li>
  <% } %>
  <% } %>
  <% for(var i=0;i<blah.length;i++) { %>
  <li>
  num: <%= blah[i].num %>
  <% if(blah[i].num==3) { %>
  <% for(var j=0;j<blah[i].inner.length;j++) { %>
  <li><%= blah[i].inner[j].time %></li>
  <% } %>
  <% } %>
  </li>
  <% } %>
</ul>


语法 | mustache、handlebars

<ul>
  {{#list}}
  {{#show}}
  <li>{{name}} (index: {{index}})</li>
  {{/show}}
  {{/list}}
  {{#blah}}
  <li>
  num: {{num}}
  ...
  {{#inner}}
  <li>{{time}}</li>
  {{/inner}}
  ...
  </li>
  {{/blah}}
</ul>


语法 | kissy、juicer

<ul>
  {{#each list as it,k}}
  {{#if it.show}}
  <li>{{it.name}} (index: {{k}})</li>
  {{/if}}
  {{/each}}
  {{#each blah as it}}
  <li>
  num: {{it.num}}
  {{#if it.num==3}}
  {{#each it.inner as it2}}
  <li>{{it2.time}}</li>
  {{/each}}
  {{/if}}
  </li>
  {{/each}}
</ul>


语法 | kissy、juicer

<ul>
  {@each data.list as it,k}
  {@if it.show}
  <li>${it.name} (index: ${k})</li>
  {@/if}
  {@/each}
  {@each data.blah as it}
  <li>
  num: ${it.num}
  {@if it.num==3}
  {@each it.inner as it2}
  <li>${it2.time}</li>
  {@/each}
  {@/if}
  </li>
  {@/each}
</ul>


立场

语法上：不赞同完全采用原生语法，也不认可过于 Logic-less 从而在性能上遇到瓶颈。
性能上：认为模板引擎的性能应该是第⼀一位的。

The basic advice regarding response times has been about the same for thirty years [Miller
1968; Card et al. 1991]:

• 0.1 second is about the limit for having the user feel that the system is reacting
instantaneously, meaning that no special feedback is necessary except to display the result.
• 1.0 second is about the limit for the user's ﬂow of thought to stay uninterrupted, even
though the user will notice the delay. Normally, no special feedback is necessary during
delays of more than 0.1 but less than 1.0 second, but the user does lose the feeling of
operating directly on the data.

100ms * 100w = 27.777hours


性能


性能 - 最大化渲染测试


性能优化点

using += instead of array.push


str += "one" + "two";

When evaluating this code, four steps are taken:

1. A temporary string is created in memory.
2. The concatenated value "onetwo" is assigned to the temporary string.
3. The temporary string is concatenated with the current value of str.
4. The result is assigned to str.

- Hign Performance Javascript


str = ["one", "two"].join(‘’);

This dramatic improvement results from avoiding repeatedly allocating memory for
and copying progressively larger and larger strings. When joining an array, the
browser allocates enough memory to hold the complete string, and never copies the
same part of the final string more than once.



Browser string optimizations have changed the string
concatenation picture.

Firefox was the first browser to optimize string concatenation. Beginning with
version 1.0, the array technique is actually slower than using the plus operator
in all cases. Other browsers have also optimized string concatenation, so Safari,
Opera, Chrome, and Internet Explorer 8 also show better performance using
the plus operator. Internet Explorer prior to version 8 didn’t have such an
optimization, and so the array technique is always faster than the plus operator.

— Writing Efficient JavaScript: Chapter 7 – Even Faster Websites


The V8 engine (used in Google Chrome) uses this code to do string
concatenation:

// ECMA-262, section 15.5.4.6
function StringConcat() {
if (IS_NULL_OR_UNDEFINED(this) && !IS_UNDETECTABLE(this)) {
throw MakeTypeError("called_on_null_or_undefined", ["String.prototype.concat"]);
}
var len = %_ArgumentsLength();
var this_as_string = TO_STRING_INLINE(this);
if (len === 1) {
return this_as_string + %_Arguments(0);
}
var parts = new InternalArray(len + 1);
parts[0] = this_as_string;
for (var i = 0; i < len; i++) {
var part = %_Arguments(i);
parts[i + 1] = TO_STRING_INLINE(part);
}
return %StringBuilderConcat(parts, len + 1, "");
}


性能优化点

avoid using with block


性能优化点

cache the compiled template.


Cache The Compiled Template

JavaScript, like many scripting languages, allows you to take a string containing
code and execute it from within running code. There are four standard ways to
accomplish this: eval(), the Function() constructor, setTimeout(), and setInterval().
Each of these functions allows you to pass in a string of JavaScript code and have it
executed.



安全性

var json={
! output:'<script>alert("XSS");</script>'
};

document.write $(node).html()

juicer('${output}',json);
//输出：<script>alert("XSS");</script>

juicer('$${output}',json);
//输出：<script>alert("XSS");</script>


Juicer 的使用方法.


{@each list as it, k}
<span class=”{@if k+2>list.length}notdot{@/if}”>...</span>
{@/each}


http://taobao.com/s?q=%E6%B7%98%E5%AE%9D

json={query:’淘宝’,...}
http://taobao.com/s?q=${query|encodeURIComponent}


compile render
template reusable function html code
compiled template


单一接口

(function() {
var juicer = function() {
var args = [].slice.call(arguments);
args.push(juicer.options);

if(arguments.length == 1) {
return juicer.compile.apply(juicer, args);
}

if(arguments.length >= 2) {
return juicer.to_html.apply(juicer, args);
}
};

...
...


编译

juicer.compile = function(tpl, options) {
if(!options || options !== this.options) {
options = __creator(options, this.options);
}

try {
var engine = this.__cache[tpl] ?
this.__cache[tpl] :
new this.template(this.options).parse(tpl, options);

if(!options || options.cache !== false) {
this.__cache[tpl] = engine;
}

return engine;

} catch(e) {
__throw('Juicer Compile Exception: ' + e.message);

return {
render: function() {} //noop
};
}
};


编译

this.parse = function(tpl, options) {
var _that = this;

if(!options || options.loose !== false) {
tpl = this.__lexicalAnalyze(tpl) + tpl;
}

tpl = this.__removeShell(tpl, options);
tpl = this.__toNative(tpl, options);

this._render = new Function('_, _method', tpl);

this.render = function(_, _method) {
if(!_method || _method !== that.options._method) {
_method = __creator(_method, that.options._method);
}

return _that._render.call(this, _, _method);
};

return this;
};


before __removeShell

<ul>

  {@each list as it,k}

  {@if it.show}

  <li>${it.name} (index: ${k})</li>

  {@/if}

  {@/each}

</ul>


after __removeShell

<ul>
  <% for var i0 = 0; i0 < list; i0++ { %>
<% var it = list[i0]; %>
<% var k = i0; %>
  <% if(it.show) { %>
  <li><%= it.name %> (index: <%= k %>)</li>
  <% } %>
  <% } %>
</ul>


__toNative
function anonymous(_, _method) {
'use strict';
var _ = _ || {};
var _out = '';
_out += '';
try {
_out += '';
var list = _.list;
var it = _.it; __lexicalAnalyze
var k = _.k;
_out += '<ul>';
for (var i0 = 0, li0 = list.length; i0 < li0; i0++) {
var it = list[i0];
var k = i0;
_out += '';
if (it.show) {
_out += '<li>';
_out += _method.__escapehtml.escaping(_method.__escapehtml.detection((it.name)));
_out += ' (index: ';
_out += _method.__escapehtml.escaping(_method.__escapehtml.detection((k)));
_out += ')</li> ';
}
_out += '';
}
_out += '</ul>';
} catch (e) {
_method.__throw("Juicer Render Exception: " + e.message);
}
_out += '';
return _out;
}


渲染函数

var _that = this;

}



}

};

return this;
};


参数/方法继承

var __creator = function(o, proto) {
o = o !== Object(o) ? {} : o;

if(o.__proto__) {
o.__proto__ = proto;
return o;
}

var _Empty = function() {};
var n = new((_Empty).prototype = proto, _Empty);

for(var i in o) {
if(o.hasOwnProperty(i)) {
n[i] = o[i];
}
}

return n;
};


编译并渲染

juicer.to_html = function(tpl, data, options) {
if(!options || options !== this.options) {
options = __creator(options, this.options);
}

return this.compile(tpl, options).render(data, options._method);
};


var _that = this;

}



var fn = function() {};

fn.toString = function() {
}

};

return fn;
};

return this;
};


展望

·继续优化 Juicer （性能、源代码）

·完善更多的文档和实利

·提供其它模板语法到 Juicer 模板的自动化工具

·更多的语言支持（诸如PHP、Python、Ruby …）

·精确的模板调试模式，精确到行号和模板错误位置

·持续改进


Q&A

juicer(‘${over}’, {over:‘thanks!’});


Juicer - A fast template engine using javascript

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