如何验证 Javascript 对象数组中是否存在对象键？

Question

我有一个如下所示的数组。

cont arr= [ { id: 1, username: 'fred' }, { id: 2, username: 'bill' }, { id: 2, username: 'ted' } ]

我能知道如何验证数组对象中是否存在“用户名”吗？

Answer 1

hasOwnProperty 可用于此

let  x = {
    y: 1
};
console.log(x.hasOwnProperty("y")); //true
console.log(x.hasOwnProperty("z")); //false

更多信息请参考SO related question

Answer 2

如果你想知道数组中是否存在特定的用户名值，你可以使用Array.some()来完成

const arr= [ { id: 1, username: 'fred' }, { id: 2, username: 'bill' }, { id: 2, username: 'ted' } ]

const checkName = (arr,name) => arr.some(a => a.username === name)

console.log(checkName(arr,'bill'))
console.log(checkName(arr,'billA'))

如果只想检查数组中是否存在用户名属性，可以结合Object.keys()、Array.flat()和Array.includes()来实现

const arr= [ { id: 1, username: 'fred' }, { id: 2, username: 'bill' }, { id: 2, username: 'ted' } ]

const checkName = (arr,name) => arr.map(a =>Object.keys(a)).flat().includes(name)


console.log(checkName(arr,'username'))
console.log(checkName(arr,'username1'))

Answer 3

const arr = [ { id: 1, username: 'fred' }, { id: 2, username: 'bill' }, { id: 2, username: 'ted' } ];

// get array of usernames from array of objects
const usernames = arr.map(obj => obj.username);
console.log(usernames);
console.log(usernames.includes('bill'));
console.log(usernames.includes('paul'));