var str1 ='[{"name":"kevin","age":18},{"name":"rose","age":16}]';

String.prototype.transArray=function(){

     var str =this.replace(/\[/,'');

    var newstr = str.replace(/\]/,'');

    var arr1 = newstr.split(',');

   var jsonstr,arr2=[];

     for(var i=0;i<arr1.length;i++){

    jsonstr = arr1[i]+','+arr1[i+1];

   arr2.push(JSON.parse(jsonstr));

    i++;

}

return arr2;

}

var k = str1.transArray();

console.log(k);