var employees = [
    {"idEmployee":"1", "name":"Matheus","surname":"Verissimo"},
    {"idEmployee":"2", "name":"Matheus", "surname":"Almeida"},
    {"idEmployee":"3","name": "Entao", "surname":"Queisso"}
];


var tasks =[
    {"idTask":"1", "idEmployee":"1", "desc":"ruby"},
    {"idTask":"2", "idEmployee":"1", "desc":"css"},
    {"idTask":"3", "idEmployee":"2", "desc":"java"},
    {"idTask":"4","idEmployee": "3", "desc":"html"}
];

var newEmployees = [];

for (var position = 0; position <  employees.length; position++) {
    var idEmployee = employees[position].idEmployee;

    for(var positionTasks = 0; positionTasks <  tasks.length; positionTasks++){
        var idEmployeeTask = tasks[positionTasks].idEmployee;
        if(idEmployeeTask == idEmployee ){

        var obj = $.extend({},employees[position],tasks[positionTasks]);
            newEmployees.push(obj);

        }
    }

}
console.log(JSON.stringify(newEmployees))