converts XPath indexed-repeat( ) to a positioned path - indexed-repeat(/path/to/repeat/node, /path/to/repeat, 3) -> /path/to/repeat[position() = 3]/node

convertIndexRepeatToPositionedPath

    /**
     * Converts an indexed-repeat(node, path, position, path, position, etc) to its native XPath
     * equivalent using [position() = x] predicates
     *
     * @param  {string} expr the XPath expression
     * @return {string}      converted XPath expression
     */
    FormModel.prototype.convertIndexedRepeatToPositionedPath = function( expr ) {
        var indexedRepeats = expr.match( /(indexed-repeat\s?\([^\)]+\))/g );

        if ( !indexedRepeats ) {
            return expr;
        }

        indexedRepeats.forEach( function( indexedRepeat, irIndex ) {
            var i, positionedPath,
                params = indexedRepeat.replace( /indexed-repeat\s?\(([^\)]+)\)/g, '$1' ).split( ',' );

            if ( params.length % 2 === 1 ) {

                //trim parameters
                params.forEach( function( param, index ) {
                    params[ index ] = param.trim();
                } );

                positionedPath = params[ 0 ];

                for ( i = params.length - 1; i > 1; i -= 2 ) {
                    positionedPath = positionedPath.replace( params[ i - 1 ], params[ i - 1 ] + '[position() = ' + params[ i ] + ']' );
                }
                expr = expr.replace( indexedRepeat, positionedPath );

            } else {
                console.error( 'indexed repeat with incorrect number of parameters found', indexedRepeat );
                return "'Error with indexed-repeat parameters'";
            }
        } );
        return expr;
    };