juicer - a fast template engine using javascript

一个前端 Javascript 模板引擎的实现与优化

流火 @ TaobaoUEDBlog: http://benben.cc

12年5月28日星期⼀一

http://benben.cc

http://benben.cc

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】


Mustache

Kissy template

jQuery tmpl

nTenjin

...micro template

ejsdoT yayaTemplate

artTemplatehandlebar


is it nessary ? are u sure ?

如无必要，勿增实体


Juicer 的特点

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

support node.js only 5kb


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。

模板引擎基本原理

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


JSON TemplateTemplateEngine

HTMLFragment

water juicer fruits


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


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

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

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

拼字符串


Syntax Performance

SecurityXSS escape

Error Handling

easy to write & read as faster as you can

robustness


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

jQuery Tmpl、kissy Template

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

追求纯粹，希望通过原生的

Javascript 语法来写模板，这类模

板引擎的实现一定是编译型的，

但是它们的写法往往让人抓狂。

追求 KISS / Logic less, 这注定了这

类模板引擎的实现是解释型的，

也就注定了它们性能是有瓶颈

的。

语法

{{#list}}

{{#a}} {{value}} {{/a}}


JSON HTML

var data={ list:[ {name:'liuhuo',show:true}, {name:'benben',show:false}, {name:'taobao',show:true} ], blah:[ {num:1}, {num:2}, {num:3,inner:[ {'time':'15:00'}, {'time':'16:00'}, {'time':'17:00'}, {'time':'18:00'} ]}, {num:4} ]};

<ul> <li>liuhuo (index: 0)</li> <li>taobao (index: 2)</li> <li>num: 1</li> <li>num: 2</li> <li>num: 3</li> <li>15:00</li> <li>16:00</li> <li>17:00</li> <li>18:00</li> <li>num: 4</li></ul>


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>


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。

立场

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


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";


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.


str = ["one", "two"].join(‘’);


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


http://oreilly.com/server-administration/excerpts/even-faster-websites/writing-efficient-javascript.html

http://oreilly.com/server-administration/excerpts/even-faster-websites/writing-efficient-javascript.html

// ECMA-262, section 15.5.4.6function 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, "");}

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


http://v8.googlecode.com/svn/trunk/src/string.js

http://v8.googlecode.com/svn/trunk/src/string.js

性能优化点

avoid using with block


性能优化点

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.


Cache The Compiled Template


安全性

var json={

! output:'<script>alert("XSS");</script>'

};

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

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

document.write $(node).html()


Juicer 的使用方法.


http://juicer.name

http://juicer.name

{@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}




http://taobao.com/s?q=%7B

http://taobao.com/s?q=%7B

template reusable function html codecompiled template

compile render


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; };

编译


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; 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;}

__lexicalAnalyze


渲染函数




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


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; };


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);

};

编译并渲染





this.render = function(_, _method) { var fn = function() {};

fn.toString = function() { if(!_method || _method !== that.options._method) { _method = __creator(_method, that.options._method); }


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


juicer(‘${over}’, {over:‘thanks!’});

Q & A


juicer - a fast template engine using javascript

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