preset-statements.js

var EACH = / *([^,]+)(\s*,\s*([\S]+))? in (\S+)/

module.exports = {
  if: function (expression, scope, renderContent, renderOtherwise) {
    if( this.eval(expression)(scope) ) return renderContent(scope)
    return renderOtherwise(scope)
  },
  each: function (expression, scope, renderContent) {
    var expressions = expression.match(EACH), key, i, n, s

    if( !expressions ) throw new Error('each expression is not correct: ' + expression )

    var result = '',
        item_key = expressions[1],
        items = this.eval(expressions[4])(scope),
        i_key = expressions[3] || ( items instanceof Array ? '$index' : '$key' )

    if( !items || ( !(items instanceof Array) && typeof items !== 'object' ) ) throw new TypeError('list in expression should be a non null Object or an Array')

    if( items instanceof Array ) {
      for( i = 0, n = items.length ; i < n ; i++ ) {
        s = Object.create(scope)
        s[i_key] = i
        s[item_key] = items[i]
        result += renderContent(s)
      }
    } else {
      for( key in items ) {
        s = Object.create(scope)
        s[i_key] = key
        s[item_key] = items[key]
        result += renderContent(s)
      }
    }

    return result
  },
}