gistfile1.txt

const calculateExecutionTimes = (input) => {
    const map = {};
    
    for(let i=0; i < input.length; i++) {
        const item = input[i];
        if(map[item.name]) {
            map[item.name] = Math.abs(item.time - map[item.name]);
        } else {
            map[item.name] = item.time;
        }
    }
    
    return map;
}

const input = [
    { name: "main", time: 25, event: "end" },
    { name: "main", time: 0, event: "start" },
    { name: "subTask1", time: 5, event: "start" },
    { name: "subTask2", time: 15, event: "start" },
    { name: "subTask2", time: 20, event: "end" },
]

console.log(calculateExecutionTimes(input));