Array of objects comparision in javascript

Hi,
I have  array like
a=[{"name":"prudhvi","id":10,"age":30},{"name":"sai","id":20,"age":25},{"name":"sai","id":21",age":20},{"name":"pavan","id":20,"age":15},{"name":"Prudhvi","id":20,"age":10}];
I want unique items based on name and id, irrespective of age. Please give me some idea...
I had tried like

for( i = 0; i < a.length; i++) {
  for( j = i+1;j < a.length; j++) {
      if ( a[i].name != a[j].name) {
       if(a[i].id == a[j].id) {
       a.splice(i,1);
       a.splice(j,1);
}
}
else {
a.splice(i,1);
b.splice(j,1);
}
}
< ...