code: function( src, fileName ) {
          var results = [];
          var identifiers = [];
          var ast = parse(src, fileName);
          walk.simple(ast, {
              Identifier: function( node ) {
                  identifiers.push( node );
              }
          });
  
          for( var i = 0, len = identifiers.length; i < len; ++i ) {
              var id = identifiers[i];
              if( ignore.indexOf(id) > -1 ) {
                  continue;
              }
              var constant = constants[id.name];
              if( constant === void 0 ) {
                  continue;
              }
              if( constant.identifier === id ) {
                  continue;
              }
  
              results.push( new ConstantReplacement( constant.value, id.start, id.end ) );
  
          }
          return convertSrc( src, results );
      }
docs: Expand constants in normal source files