Proper JavaScript code templating with source maps support.

This module allows to generate JavaScript AST from code template and AST nodes as substitutions.

This is more proper way of code templating since it works on AST not on code string, and thus preserves locations which allow to generate source maps in future.

Install the module with: npm install estemplate and require it:

npm i estemplate --save

var estemplate = require('estemplate');

Generates SpiderMonkey AST from given template string, optional esprima options and data.

Supported template substitution markers:

• Compile-time execution block: <% var localCounter = 0; %>
• Node substitution: var x = <%= expr %> + 1;
• Array elements: var a = [%= elements %];
• Function parameters: function f(%= params %) {}
• Call arguments: var x = f(%= args %);
• Block statements: define(function () {%= body %});
• Literals: var x = "%= 'alpha' + 'beta' %";

You can combine list substitutions with inline elements like:

• var a = [0, %= numbers %, Infinity];
• function f(%= params %, callback) {}
• define(function () { console.time('Module'); %= body %; console.timeEnd('Module'); });

From template, you can access entire data object via it and estemplate itself via estemplate.

If you set options.fast to true, then passed data will be available only via it variable, but template function in general will be significantly faster.

Same as above but returns function that can be reused for AST generation (just save result and call with data as argument whenever needed).

var ast = estemplate('var <%= varName %> = <%= value %> + 1;', {
  varName: {type: 'Identifier', name: 'myVar'},
  value: {type: 'Literal', value: 123}
});

console.log(escodegen.generate(ast));
// > var myVar = 123 + 1;

template.jst

define(function (require, exports, module) {% = body %});

index.js

var dependency1 = require('dependency1'),
    dependency2 = require('dependency2');

module.exports = function () {
	return dependency1() + dependency2();
};

main code

var templateCode = fs.readFileSync('template.jst', 'utf-8');
var template = estemplate.compile(templateCode, {attachComment: true});

var program = esprima.parse(fs.readFileSync('index.js', 'utf-8'), {
    loc: true,
    source: 'index.js'
});

var ast = template({body: program.body});

var output = escodegen.generate(ast, {
  sourceMap: true,
  sourceMapWithCode: true
});

console.log(output.code);

output

define(function (require, exports, module) {
    var dependency1 = require('dependency1'), dependency2 = require('dependency2');
    module.exports = function () {
        return dependency1() + dependency2();
    };
});

In lieu of a formal styleguide, take care to maintain the existing coding style. Add unit tests for any new or changed functionality. Lint and test your code using Grunt.

Copyright (c) 2014 Ingvar Stepanyan. Licensed under the MIT license.