<script>
var arr1 = [{id: 12,name: 20}, {id: 13,name: 30}];
var arr2 = [{id: 12,title: 500}, {id: 13,title: 666}];
for(var i=0;i<arr1.length;i++){
for(var j=0;j<arr2.length;j++){
if(arr1[i].id===arr2[j].id){
arr1[i].title=arr2[j].title;
break;
}
}
}
console.log(arr1);
</script>