javascript - 如何使用javascript访问JSON数据库

Question

如何使用 JavaScript 找到值为“Anna”的“名字”并在末尾显示她的“姓氏”？这只是一个虚拟示例，供我理解它是如何工作的。

var employees = [
    {
    "firstName":"John",
    "lastName":"Doe"
    }, 
    {
    "firstName":"Anna",
    "lastName":"Smith"
    },
    {
    "firstName":"Peter",
    "lastName":"Jones"
    }
];

document.getElementById("demo").innerHTML =
employees.firstName;

<p id="demo"></p>

Answer 1

您必须迭代并检查该值，然后执行您想要的操作:

for (var i = 0; i < employees.length; i++) {
    if (employees[i].firstName == "Anna") {
        document.getElementById("demo").innerHTML = employees[i].lastName;
        break;
    }
}

要显示超过 1 个 Anna - 我会在数组上使用 filter，然后join:

var lastNames = employees.filter(function(employee) {
    return employee.firstName == "Anna";
}).map(function(employee) {
    return employee.lastName;
}).join(",");

document.getElementById("demo").innerHTML = lastNames;