babel-plugin-ceval

babel-plugin-ceval

This plugin allows Babel to execute ceval functions at compile time.

API

ceval(expression: string)

Return value is used as is, it cannot return code fragments.

ceval(fn: function([args..])[, args..])

If it returns a string, it is expected to be a code fragment. If you need to return a string value, simply enclose it with quotations.

Examples

// In:
var envPath = ceval('process.env.PATH');
// Out:
var envPath = '/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games';

// In:
var dirname = ceval('__dirname');
// Out:
var dirname = '/home/arash16/Projects/ceval-test';

// In:
var version = ceval('require("./package.json").version');
// Out:
var version = '1.0.0';

// In:
ceval(function() {
	var r = '';
	for (var i=0; i<4; ++i)
		r += 'console.log('+i+');';
	return r;
});
// Out:
console.log(0);console.log(1);console.log(2);console.log(3);

// In:
var code = ceval(function() {
	var r = '';
	for (var i=0; i<3; ++i)
		r += 'console.log('+i+');';
	return '"' + r + '"';
});
// Out:
var code = 'console.log(0);console.log(1);console.log(2);';

// In:
ceval(function() {
	if (process.env.DEBUG)
		return function checker(x) { 
			return x>2; 
		};
	
	return function checker(x) { 
		return x>0; 
	};
});
// Out:
function checker(x) {
	return x > 0;
}

Installation

npm install --save-dev babel-plugin-ceval

Usage

Via .babelrc (Recommended)

.babelrc

{
  "plugins": ["ceval"]
}

Via CLI

babel --plugins ceval script.js

Via Node API

require("babel-core").transform("code", {
  plugins: ["ceval"]
});