estemplate

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.

Getting Started

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

npm i estemplate --save

var estemplate = require('estemplate');

API

estemplate(tmplString, [options], data)

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 %});

estemplate.compile(tmplString, [options])

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

Examples

Simple generation

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;

Advanced generation (with source map)

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

/** Simplified CommonJS wrapper */                                                  
define(function (require, exports, module) {
    var dependency1 = require('dependency1'), dependency2 = require('dependency2');
    module.exports = function () {
        return dependency1() + dependency2();
    };
});

Contributing

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.

License

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