有一个JS数组,如: var arr = [["projectname1","projectnumber1"],["projectname2","projectnumber2"],["projectname3","projectnumber3"]]; 想将此数组转换成JSON字符串,如: var jsonarr = [{"projectname":projectname1,"projectnumber":projectnumber1},{"projectname":projectname2,"projectnumber":projectnumber2},{"projectname":pr