Exposing the eval code in the API or the doc

[hmalphettes]

Hi there, jsep looks wonderful.

One thing that might be obvious to people familiar with esprima is that it is trivial to evaluate the generated AST:

var do_eval = function(node) {
  if(node.type === "BinaryExpression") {
    return binops[node.operator](do_eval(node.left), do_eval(node.right));
  } else if(node.type === "UnaryExpression") {
    return unops[node.operator](do_eval(node.argument));
  } else if(node.type === "Literal") {
    return node.value;
  }
};

I found it in the tests and it was not obvious to me.

I hope this helps
Many thanks!

[matthewmueller]

Wrote this module to help with this. It doesn't eval, but it'll generate a string: https://github.com/lapwinglabs/jsepgen

[oliverjanik]

Thank you for this!

[donmccurdy]

I just put together a small module for evaluation and compilation.

Evaluation:

// Evaluation
expr.eval('a + b / c', {a: 2, b: 2, c: 5}); // 0.8

Compilation:

const fn = expr.compile('foo.bar + 10');
fn({foo: {bar: 'baz'}}); // 'baz10'

There's not much to it, besides what's already shown in the tests and explained above. @soney, would you take a PR adding those functions to the core library? Or, if this doesn't exist elsewhere, would you prefer that it remain a separate repo with attribution to jsep?

[donmccurdy]

I should add — even though the module above avoids use of eval() for execution, there are still security risks you should be aware of when using it.