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":projectname3,"projectnumber":projectnumber3}];

方法如下：

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);
}