JS中的数组转变成JSON格式字符串的方法

var arr = [["projectname1","projectnumber1"],["projectname2","projectnumber2"],["projectname3","projectnumber3"]]; 

var jsonarr = [{"projectname":projectname1,"projectnumber":projectnumber1},{"projectname":projectname2,"projectnumber":projectnumber2},{"projectname":projectname3,"projectnumber":projectnumber3}]; 

function tojson(arr){   if(!arr.length) return null;   var i = 0;   len = arr.length,   array = [];   for(;i<len;i++){     array.push({"projectname":arr[i][0],"projectnumber":arr[i][1]});   }   return JSON.stringify(array); }