/*jshint expr:true */
/**
Adds the `Y.Template.Micro` template engine, which provides fast, simple
string-based micro-templating similar to ERB or Underscore templates.
@module template
@submodule template-micro
@since 3.8.0
**/
/**
Fast, simple string-based micro-templating engine similar to ERB or Underscore
templates.
@class Template.Micro
@static
@since 3.8.0
**/
// This code was heavily inspired by Underscore.js's _.template() method
// (written by Jeremy Ashkenas), which was in turn inspired by John Resig's
// micro-templating implementation.
var Micro = Y.namespace('Template.Micro');
/**
Default options for `Y.Template.Micro`.
@property {Object} options
@param {RegExp} [options.code] Regex that matches code blocks like
`<% ... %>`.
@param {RegExp} [options.escapedOutput] Regex that matches escaped output
tags like `<%= ... %>`.
@param {RegExp} [options.rawOutput] Regex that matches raw output tags like
`<%== ... %>`.
@param {RegExp} [options.stringEscape] Regex that matches characters that
need to be escaped inside single-quoted JavaScript string literals.
@param {Object} [options.stringReplace] Hash that maps characters matched by
`stringEscape` to the strings they should be replaced with. If you add
a character to the `stringEscape` regex, you need to add it here too or
it will be replaced with an empty string.
@static
@since 3.8.0
**/
Micro.options = {
code : /<%([\s\S]+?)%>/g,
escapedOutput: /<%=([\s\S]+?)%>/g,
rawOutput : /<%==([\s\S]+?)%>/g,
stringEscape : /\\|'|\r|\n|\t|\u2028|\u2029/g,
stringReplace: {
'\\' : '\\\\',
"'" : "\\'",
'\r' : '\\r',
'\n' : '\\n',
'\t' : '\\t',
'\u2028': '\\u2028',
'\u2029': '\\u2029'
}
};
/**
Compiles a template string into a JavaScript function. Pass a data object to the
function to render the template using the given data and get back a rendered
string.
Within a template, use `<%= ... %>` to output the value of an expression (where
`...` is the JavaScript expression or data variable to evaluate). The output
will be HTML-escaped by default. To output a raw value without escaping, use
`<%== ... %>`, but be careful not to do this with untrusted user input.
To execute arbitrary JavaScript code within the template without rendering its
output, use `<% ... %>`, where `...` is the code to be executed. This allows the
use of if/else blocks, loops, function calls, etc., although it's recommended
that you avoid embedding anything beyond basic flow control logic in your
templates.
Properties of the data object passed to a template function are made available
on a `data` variable within the scope of the template. So, if you pass in
the object `{message: 'hello!'}`, you can print the value of the `message`
property using `<%= data.message %>`.
@example
YUI().use('template-micro', function (Y) {
var template = '<ul class="<%= data.classNames.list %>">' +
'<% Y.Array.each(data.items, function (item) { %>' +
'<li><%= item %></li>' +
'<% }); %>' +
'</ul>';
// Compile the template into a function.
var compiled = Y.Template.Micro.compile(template);
// Render the template to HTML, passing in the data to use.
var html = compiled({
classNames: {list: 'demo'},
items : ['one', 'two', 'three', 'four']
});
});
@method compile
@param {String} text Template text to compile.
@param {Object} [options] Options. If specified, these options will override the
default options defined in `Y.Template.Micro.options`. See the documentation
for that property for details on which options are available.
@return {Function} Compiled template function. Execute this function and pass in
a data object to render the template with the given data.
@static
@since 3.8.0
**/
Micro.compile = function (text, options) {
/*jshint evil:true */
var blocks = [],
tokenClose = "\uffff",
tokenOpen = "\ufffe",
source;
options = Y.merge(Micro.options, options);
// Parse the input text into a string of JavaScript code, with placeholders
// for code blocks. Text outside of code blocks will be escaped for safe
// usage within a double-quoted string literal.
//
// $b is a blank string, used to avoid creating lots of string objects.
//
// $v is a function that returns the supplied value if the value is truthy
// or the number 0, or returns an empty string if the value is falsy and not
// 0.
//
// $t is the template string.
source = "var $b='', $v=function (v){return v || v === 0 ? v : $b;}, $t='" +
// U+FFFE and U+FFFF are guaranteed to represent non-characters, so no
// valid UTF-8 string should ever contain them. That means we can freely
// strip them out of the input text (just to be safe) and then use them
// for our own nefarious purposes as token placeholders!
//
// See http://en.wikipedia.org/wiki/Mapping_of_Unicode_characters#Noncharacters
text.replace(/\ufffe|\uffff/g, '')
.replace(options.rawOutput, function (match, code) {
return tokenOpen + (blocks.push("'+\n$v(" + code + ")+\n'") - 1) + tokenClose;
})
.replace(options.escapedOutput, function (match, code) {
return tokenOpen + (blocks.push("'+\n$e($v(" + code + "))+\n'") - 1) + tokenClose;
})
.replace(options.code, function (match, code) {
return tokenOpen + (blocks.push("';\n" + code + "\n$t+='") - 1) + tokenClose;
})
.replace(options.stringEscape, function (match) {
return options.stringReplace[match] || '';
})
// Replace the token placeholders with code.
.replace(/\ufffe(\d+)\uffff/g, function (match, index) {
return blocks[parseInt(index, 10)];
})
// Remove noop string concatenations that have been left behind.
.replace(/\n\$t\+='';\n/g, '\n') +
"';\nreturn $t;";
// If compile() was called from precompile(), return precompiled source.
if (options.precompile) {
return "function (Y, $e, data) {\n" + source + "\n}";
}
// Otherwise, return an executable function.
return this.revive(new Function('Y', '$e', 'data', source));
};
/**
Precompiles the given template text into a string of JavaScript source code that
can be evaluated later in another context (or on another machine) to render the
template.
A common use case is to precompile templates at build time or on the server,
then evaluate the code on the client to render a template. The client only needs
to revive and render the template, avoiding the work of the compilation step.
@method precompile
@param {String} text Template text to precompile.
@param {Object} [options] Options. If specified, these options will override the
default options defined in `Y.Template.Micro.options`. See the documentation
for that property for details on which options are available.
@return {String} Source code for the precompiled template.
@static
@since 3.8.0
**/
Micro.precompile = function (text, options) {
options || (options = {});
options.precompile = true;
return this.compile(text, options);
};
/**
Compiles and renders the given template text in a single step.
This can be useful for single-use templates, but if you plan to render the same
template multiple times, it's much better to use `compile()` to compile it once,
then simply call the compiled function multiple times to avoid recompiling.
@method render
@param {String} text Template text to render.
@param {Object} data Data to pass to the template.
@param {Object} [options] Options. If specified, these options will override the
default options defined in `Y.Template.Micro.options`. See the documentation
for that property for details on which options are available.
@return {String} Rendered result.
@static
@since 3.8.0
**/
Micro.render = function (text, data, options) {
return this.compile(text, options)(data);
};
/**
Revives a precompiled template function into a normal compiled template function
that can be called to render the template. The precompiled function must already
have been evaluated to a function -- you can't pass raw JavaScript code to
`revive()`.
@method revive
@param {Function} precompiled Precompiled template function.
@return {Function} Revived template function, ready to be rendered.
@static
@since 3.8.0
**/
Micro.revive = function (precompiled) {
return function (data) {
data || (data = {});
return precompiled.call(data, Y, Y.Escape.html, data);
};
};
