respuesta-test.js

let items = [
	{name:"A", value:2},	
	{name:"B", value:3},
	{name:"A", value:4},
];

let result = [];

items.map((item, index) => {

  let res = result.find(res => res.name === item.name);
  if (res) {
    res.value += item.value;
  } else {
    result.push(item);
  }

});

console.log(result);