How to change the alignment of text using javascript?

Hi,
I need to change the alignment of text to center.

for (var i = 1 ; i <= graphNumberOfLines + 1; i++)
            {
               var ii=i;
               ii= doc.textFrames.add();  //adding text
               ii.textRange.characterAttributes.size = 8;  //character size for text
               ii.textRange.characterAttributes.textFont = app.textFonts.getByName("Times-Roman");
                ii.textRange.StyleRunAlignmentType = "Center";
               ii.top = firstPoint[1]+yGraphInc;  //x coordinate for the new value
               ii.left = firstPoint[0]+xGraphInc;  //y coordinate for the new value
               finalContent=Number(graphFirstValue)+graphIncValue;
               finalContent=finalContent.toString();
               var finalContentcheck=Number(finalContent.indexOf("-"));
               if(finalContentcheck>=0){
                   finalContent=finalContent.replace(/-/g,"–");  
               }
               ii.contents=(finalContent);  //content for the text frame
               xGraphInc=(xGraphDiff/graphNumberOfLines)*i;  //incrementing the x coordinate
               yGraphInc=(yGraphDiff/graphNumberOfLines)*i;  //incrementing the y coordinate
               if(graphValues[1]>=0){
                    graphIncValue=graphIncValue+graphIncrement;  //incrementing the content
               }else{
                   graphIncValue=graphIncValue-graphIncrement;  //incrementing the content
               }
            } 

This is how I am writing in the document. I need to align just after writing.
Thanks in advance.