下边放上我写的TS代码：

 private Index(MainString:string,SubString:string):number
    {
    
    
       if(MainString==null||SubString==null)
       {
    
    
           return -1;
       }
       
       
       let MainStringLength:number=MainString.length;
       let SubStringLength:number=SubString.length;
       console.log("MainStringLength:"+MainStringLength);
       console.log("SubStringLength:"+SubStringLength);

       let pos=-1;
       let prepos=pos;

       let i=0;
       let j=0;
     
       while(i<MainStringLength&&j<SubStringLength)
       {
    
    
           if(MainString[i]==SubString[j])
           {
    
    
               ++i;
               ++j;
           }
           else
           {
    
    
               i=i-j+1;
               j=0;
           }
       }
       if(j==SubStringLength)
       {
    
    
           prepos=pos;
           pos=i-j;
       }

        return pos+1;

    }