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JavaScript function rewriter, for little DSLs
PogoScript JavaScript
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README.md

dslify

Rewrites a JavaScript function, such that any global property access is transformed to call a member of a dsl argument. Use dslify to build small domain-specific languages and configuration utilities.

Dependency status

Install

npm install dslify

Example

var dslify = require('dslify');

var fn = function() { return shout(word); };
var shouter = dslify.transform(fn);

var dsl = {
    shout: function(something) {
        return something + "!!";
    },
    word: "unicorns"
};
shouter(dsl); // unicorns!!

Strings Example

Sometimes you might want to operate with strings instead of JavaScript functions. For example if you are generating templates or want to send JavaScript to the client.

var dslify = require('dslify');

var input = "function(input) { return shout(input, globalValue); };";
var output = dslify.transform(input, {asString: true});

output // function(input) { return shout(input, _dsl.globalValue); };

How?

dslify parses functions using esprima, rewriting them as new functions using escodegen.

Hold on, isn't this just a long-winded JavaScript 'with'?

Yes. But 'with' is leaky and dangerous, wheras dslify is like a sandbox because it rewrites access to global scope, e.g:

var dslify = require('dslify');

var dsl = {};

var withWith = function(dsl) {
    with (dsl) {
        y = 'leaks into global!';
    }
};
var withDslify = dslify.transform(function() {
    z = 'global is safe!';
});

withWith(dsl);
withDslify(dsl);

console.log(global.y);  // leaks into global!
console.log(global.z);  // undefined
console.log(dsl.z);     // global is safe!

Isn't it hard to debug dynamically-generated functions?

Yes. So depending on how much debugging you do, runtime function rewriting may only be practical with 'configuration' DSLs that are unlikely to generate errors. For bigger DSLs you might consider rewriting functions to disk, as a compilation step in your build process.

License

BSD

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