eslisp SXML macro implementation example

readme.markdown

eslisp SXML macro implementation example

The module eslsxml.js exports a macro that reads its arguments as SXML syntax (partially implemented), and outputs a string with the equivalent XML.

This eslisp code (with the first SXML example from Wikipedia)—

(macro sxml (require "./eslsxml.js"))

((. console log)
 (sxml
  (tag (@ (attr1 "value1")
          (attr2 "value2"))
       (nested "Text node")
       (empty))))

—compiles to JavaScript as—

console.log('<tag attr1="value1" attr2="value2"><nested>Text node</nested><empty></empty></tag>');

Implementation hints for compiling to virtual DOM instead of a string

The example code could be adapted to return estree objects representing the appropriate function calls at line 41. Eslisp understands the more complex estree spec just as well as its own dead-simple {type: "string", value: 'whatever'} S-expression AST type.

eslsxml.js

function convertToplevel(node) {
  switch (node.type) {

    case 'string':
      return node.value

    case 'list':
      var name = node.values[0].value
      var rest = node.values.slice(1)

      var attributes = []
      var childNodes = []
      rest.forEach(function(x) {
        if ((x.type === 'list')
            && (x.values[0].value === '@')
            && (x.values[0].type === 'atom')) {
          x.values.slice(1).forEach(function(attrPair) {
            var key   = attrPair.values[0].value
            var value = attrPair.values[1].value
            attributes.push(key + '="' + value + '"')
          })
        } else {
          childNodes.push(convertToplevel(x))
        }
      })

      var attributesString = attributes.join(' ')
      var opening = '<' + name
        + (attributesString.length === 0 ?  '' : ' ')
        + attributesString + '>'
      var closing = '</' + name + '>'

      return opening + childNodes.join('') + closing

  }
}

module.exports = function() {
  var args = Array.prototype.slice.call(arguments)
  var stringified = args.map(convertToplevel).join('')
  return {
    type: 'string',
    value: stringified
  }
}