jseval

Compile time function evaluator for javascript and AST

Examples

Basic Usage

Simple usage for jseval

const evalFunctions = {
    $my_fn:  function( id ) { return 'my_id_'+id; },
    $inline: function( fn ) { return fn(); },
};
const src = `
  var x = 10;
  var y = $my_fn(30);
  var z = $inline(function() {
    var ary = [];
    for ( var i = 0; i < 100; ++i )
      ary.push( i );
    return ary;
  });
`;
jseval( src, evalFunctions )  
    .then(function( output ) {
        /*
         Expected Output:
         var x = 10;
         var y = 'my_id_30';
         var z = [0,1,2,3,4,...,99];
         */
        console.log( output );
    });

Async

Async evaluation

const evalFunctions = {
    $async:  function() { 
        return Promise.delay(1000)
            .then(function() { return 'async value'; }
        ;
    },
};
const src = `
  var x = $async();
`;
jseval( src, evalFunctions )  
    .then(function( output ) {
        /*
         Expected Output after 1000ms delay:
         var x = 'async value';
         */
        console.log( output );
    });

Eval Functions

An eval function is a function to be compiled by jsval. It allows the return of promises to defer its evaluation.

const evalFunctions = {
    $include: function( filename ) {
        return /* some promise that reads the file */;
    }
}

Methods

jseval( src, evalFunctions, options )

Source to source evaluation

• src {String}: The string to be evaluated
• evalFunctions {object}: A map of functions to be runned when encountered
• options {object}:
  • options.source {string}: If passed, the string will be used as a source filename for sourcemap generation
  • options.Promise {object}: The Promise library to be used (must have at least Promise.all, Promise.resolve)

Returns {Promise} A promise with the output string if no source-map is requested. Otherwise an object with code and map properties.

jseval.evalAST( ast, evalFunctions, options )

AST to AST evaluation

• ast {object}: The AST to be evaluated