Matrix shift and unshift prototype

gistfile1.js

    function shift(){
      var yLen = mx.length,
        row;

      if(yLen > 0){
        row = mx[0];

        if(row.length > 0){
          return row.shift();
        }else{
          mx.shift();

          return this.shift();
        }
      }
    }

    function unshiftRows(yIndex, row, val){
      var nextIndex = ++yIndex;
      row.unshift(val);

      while(nextIndex < this.mx.length){
        if(row.length > this.x){
          val = row.pop();
          row = this.mx[nextIndex];
          row.unshift(val);
        }else{
          this.mx.push([val]);
        }
        ++nextIndex;
      }
    }

    function unshift(val){
      var yLen = mx.length,
        row, xLen;

      if(yLen > 0){
        // get the last row
        row = mx[0];
        row.unshift(val);
        xLen = row.length;

        if(xLen > this.x){
          // need to push the next row
          if(2 <= mx.length){
            unshiftRows(1, mx[1], row.pop());
          }else{
            mx.push([row.pop()]);
          }
        }
      }else{
        mx.unshift([val]);
      }
    }

still pondering the usage of an unshift method and the associated overhead with re-organizing the matrix