The document discusses various techniques for optimizing JavaScript template engines, including: - Using string concatenation instead of array pushing to build output for better performance - Avoiding the "with" construct to prevent unnecessary overhead - Caching compiled templates to avoid repeated compilation The document provides examples comparing different template engines and approaches, and benchmarks performance on sites like jsperf. It focuses on techniques to improve template engine syntax, security, error handling and performance.

2. Juicer
一个 Javascript 模板引擎の实现与优化
流火 @ TaobaoUED
Blog: http://benben.cc

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

4. var json={
name:"liuhuo",
blog:"ued.taobao.com"
};
<span class="name">流火 (blog: ued.taobao.com)</span>

5. var json={
name:"liuhuo",
blog:"ued.taobao.com"
};
<span class="name">流火 (blog: ued.taobao.com)</span>
var html;
html='<span class="name">'+json.name+' (blog: '+json.blog+')</span>';

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

8. var tpl='<span class="name">{name} (blog: {blog})</span>';
var html=sub(tpl,json);

9. YUI.Lang.sub

10. JSON Template

11. JSON Template

12. JSON Template
Engine Template

13. JSON Template
Engine Template

14. JSON Template
Engine Template

15. JSON Template
Engine Template
HTML
Fragment

16. water juicer fruits
JSON Template
Engine Template
HTML
Fragment

18. doT yayaTemplate
ejs
Mustache
artTemplate
nTenjin
Kissy template
micro template
...
jQuery tmpl

20. “如无必要，勿增实体”
Entia non sunt multiplicanda praeter
necessitatem.

22. Security

23. Security
XSS escape

24. Security
XSS escape
Syntax

25. Security
XSS escape
Syntax
easy to write & read

26. Security
XSS escape
Syntax Performance
easy to write & read

27. Security
XSS escape
Syntax Performance
easy to write & read as faster as you can

28. Security
XSS escape
Syntax Performance
easy to write & read as faster as you can
Error Handling

29. Security
XSS escape
Syntax Performance
easy to write & read as faster as you can
Error Handling
robustness

30. Security
XSS escape
Syntax Performance
easy to write & read as faster as you can
Error Handling
robustness

31. Syntax
<ul> <ul> <ul>
{{#list}} {@each data.list as it,k} {{#each list as it,k}}
{{#show}} {@if it.show} {{#if it.show}}
<li>{{name}} (index: {{index}})</li> <li>${it.name} (index: ${k})</li> <li>{{it.name}} (index: {{k}})</li>
{{/show}} {@/if} {{/if}}
{{/list}} {@/each} {{/each}}
{{#blah}} {@each data.blah as it} {{#each blah as it}}
<li> <li> <li>
num: {{num}} num: ${it.num} num: {{it.num}}
... {@if it.num==3} {{#if it.num==3}}
{{#inner}} {@each it.inner as it2} {{#each it.inner as it2}}
<li>{{time}}</li> <li>${it2.time}</li> <li>{{it2.time}}</li>
{{/inner}} {@/each} {{/each}}
... {@/if} {{/if}}
</li> </li> </li>
{{/blah}} {@/each} {{/each}}
</ul> </ul> </ul>
<ul> <ul>
<% for(var i=0;i<list.length;i++) { %> <?js for(var i=0;i<it.list.length;i++) { ?>
<% if(list[i].show) { %> <?js if(it.list[i].show) { ?>
<li><%= list[i].name %> (index: <%= i %>)</li> <li>${it.list[i].name} (index: ${i})</li>
<% } %> <?js } ?>
<% } %> <?js } ?>
<% for(var i=0;i<blah.length;i++) { %> <?js for(var i=0;i<it.blah.length;i++) { ?>
<li> <li>
num: <%= blah[i].num %> num: ${it.blah[i].num}
<% if(blah[i].num==3) { %> <?js if(it.blah[i].num==3) { ?>
<% for(var j=0;j<blah[i].inner.length;j++) { %> <?js for(var j=0;j<it.blah[i].inner.length;j++) { ?>
<li><%= blah[i].inner[j].time %></li> <li>${it.blah[i].inner[j].time}</li>
<% } %> <?js } ?>
<% } %> <?js } ?>
</li> </li>
<% } %> <?js } ?>
</ul> </ul>

32. JSON
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}
]
};

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

35. <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>
using juicer
http://jsfiddle.net/paulguo/LpvwH/1/

36. <ul>
{{#each list as it,index}}
{{#if it.show}}
<li>{{it.name}} (index: {{index}})</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>
using kissy
http://jsfiddle.net/paulguo/yLg4Y/1/

37. <ul>
{{#list}}
{{#show}}
<li>{{name}} (index: {{index}})</li>
{{/show}}
{{/list}}
{{#blah}}
<li>
num: {{num}}
{{#inner}}
<li>{{time}}</li>
{{/inner}}
</li>
{{/blah}}
</ul>
using mustache
http://jsfiddle.net/paulguo/VCH9k/1/

38. <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>
using micro
http://jsfiddle.net/paulguo/KsDhC/1/

39. <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>
using nTenjin
http://jsfiddle.net/paulguo/W7eVV/1/

40. Performance

41. Performance
http://jsperf.com/javascript-template-engine/11

42. Performance
test result without
escape.

43. Performance
test result without
escape.

44. Performance
test result without
escape.
http://juicer.name/speedtest

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

46. Security
var json={
" output:'<script>alert("XSS");</script>'
};
document.write

47. Security
var json={
" output:'<script>alert("XSS");</script>'
};
document.write $(node).html()

48. Security
var json={
" output:'<script>alert("XSS");</script>'
};
document.write $(node).html()
juicer.to_html('${output}',json);
//输出：&lt;script&gt;alert("XSS");&lt;/script&gt;
juicer.to_html('$${output}',json);
//输出：<script>alert("XSS");</script>

49. template

50. compile
template reusable function

51. compile
template reusable function
compiled template

52. compile render
template reusable function html code
compiled template

53. var json={
list:[
{name:"benben"},
{name:"liuhuo"}
]
};
var tpl='{@each data.list as value,key}$${value.name}{@/each}';
var compiled_tpl=juicer.compile(tpl,{errorhandling:false});

54. function anonymous(data) {
var data = data || {};
var out = '';
out += '';
for (var i0 = 0, l = data.list.length; i0 < l; i0++) {
var value = data.list[i0];
var key = i0;
out += '';
out += ((value.name));
out += '';
}
out += '';
return out;
}

55. Several Optimization Point

56. Several Optimization Point
using += instead of array.push

58. 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

59. The V8 javascript 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, "");
}

60. Several Optimization Point
avoid using with {}

62. var person = { The with construct introduces an extra scope for
name: "Nicholas", the script engine to search through whenever a
age: 30 variable is referenced. This alone produces a
}; minor performance decrease. However, the
contents of that scope are not known at compile
function displayInfo(){ time, meaning that the compiler cannot optimize
var count = 5; for it, in the same way as it can with normal scopes
with(person){ (such as those created by functions).
alert(name + " is " + age);
alert("Count is " + count);
}
}
displayInfo();

63. Several Optimization Point
cache the compiled template.

64. 1 循环 {@each}…{@/each}
2 判断 {@if}…{@else if}…{@else}…{@/if}
3 变量（支持函数）${varname|function}
4 注释 {# comment here}

65. a demo, then docs.
http://juicer.name

66. Juicer Docs
juicer is a high-performance lightweight javascript template engine, the benefits of using juicer is that you
can seperate your data and the html structure. it can also running on node.js environment.
the name of juicer
if the data is fruit, the template compared to water, through the juicer will be able to put them mixed into
html code.
import juicer.js
<script type="text/javascript" src="juicer-min.js"></script>
* License
juicer is published under the apache license and hosted on github. if you find errors or typos please file an
issueor a pull request on the repository.

67. * API
> compile and render the template with given data immediately.
juicer.to_html(tpl,data,options);
> only compile the template, it'll return a reusable function for the given `template`.
var tpl=juicer.compile(tpl,options);
> render the complied template with given data.
var tpl=juicer.compile(tpl,options);
var html=tpl.render(data);
Options
{
" cache:true/false,
" loose:false/true,
errorhandling:true/false
}
cache in the options means that whether cache the pre-compiled templates.

68. * Syntax
a. ${var}
using ${} to evaluating expressions and functions.
${data.name}
${data.name|function}
let's use a demo to illustrate this usage.
var json={
" name:'benben',
" age:23
};
var inc=function(number) {
" return number+1;
};
//it'll be 'benben'
juicer.to_html('${data.name}',json);
//it'll be 24
juicer.to_html('${data.age|inc}',json);

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

70. http://taobao.com/s?q=%E6%B7%98%E5%AE%9D
json={
query:’淘宝’,
...
}
http://taobao.com/s?q=${query|encodeURIComponent}

71. escape/unescape
it is noteworthy that, for security reasons, ${output} will do escape to the output, if you
do not want it to be escaped, you can use $${output} to avoid this. for example:
var json={
" value:'<strong>juicer</strong>'
};
var escapetpl='${data.value}';
var unescapetpl='$${data.value}';
juicer.to_html(escapetpl,json); //it'll be '&lt;strong&gt;juicer&lt;/strong&gt;'
juicer.to_html(unescapetpl,json); //it'll be '<strong>juicer</strong>'

72. b. {@each} ... {@/each}
when you need iterate a list, you can use `each` like this.
{@each data.list as item}
" ${item.prop}
{@/each}
you can also get the index while eaching.
{@each data.list as item,index}
" ${item.prop}
" ${index} //index
{@/each}

73. c. {@if} ... {@else} ... {else if} ... {@/if}
you can also use if-else if you need.
{@each data.list as item,index}
" {@if index===3}
" " the index is 3, the value is ${item.prop}
" {@else}
" " the index is not 3, the value is ${item.prop}
" {@/if}
{@/each}
d. {# comment}
you can also write comments in the template code to facilitate future management.
{# some comment here}

74. * running on the Node.js environment
bash: npm install juicer
var juicer=require('juicer');
var html=juicer.to_html(tpl,data,options);

75. juicer.to_html(
‘${data.end}’,
Q&A {end:‘thanks!’}
);
http://juicer.name