javascript - 插入新元素时如何为 JavaScript 对象生成动态 id？

Question

我里面有 JavaScript 对象元素数组。这是示例:

var contacts =[{"id":1,"first":"Mike","last":"Johnson","email":"mjohnson@gmail.com","phone":"(203) 567-9055","status":1},{"id":2,"first":"John","last":"Dunn","email":"jdunn@gmail.com","phone":"(319) 451-7889","status":1},{"id":3,"first":"Lisa","last":"Morgan","email":"lmorgan@gmail.com","phone":"(508) 233-8908","status":1},{"id":4,"first":"Dave","last":"Hart","email":"dhart@gmail.com","phone":"(509) 874-9411","status":1}];

我必须在该数组中插入/更新记录。我不确定检查该数组中是否存在记录的最佳方法是什么。如果存在则更新js对象，如果不存在则生成新的id。理想情况下，id 应该是一个整数，并从 js 对象中当前最高 id 之后开始。因此，在上面的数据中，最高 id 值为 4。如果我插入新记录，新记录的 id 应该是 5。有没有用 JavaScript 实现这一点的好方法？

function saveContact(){
    var frmObject = $(this),
        frmKey = $("#frm_id").val(),
        formData = frmObject.serialize(),
        contactRecord = contacts.find(item => item.id === Number(frmKey));;

        if (contactRecord) {
            contacts[frmKey] = getJSON(frmObject.serializeArray()); // If already exist in array then update object
        }else{
            frmKey = 'generate new id';
            contacts[frmKey] = getJSON(frmObject.serializeArray()); // If doesn't exist generate new key and insert object in array 
        }
}

Answer 1

这在评论中提到过，但我会稍微充实一下。

如果您的数据是一个以 ID 而不是数组为键的对象，它将强制 ID 是唯一的，因为对象必须具有唯一的键。

例如:

var contacts =[{"id":1,"first":"Mike","last":"Johnson","email":"mjohnson@gmail.com","phone":"(203) 567-9055","status":1},{"id":2,"first":"John","last":"Dunn","email":"jdunn@gmail.com","phone":"(319) 451-7889","status":1},{"id":3,"first":"Lisa","last":"Morgan","email":"lmorgan@gmail.com","phone":"(508) 233-8908","status":1},{"id":4,"first":"Dave","last":"Hart","email":"dhart@gmail.com","phone":"(509) 874-9411","status":1}];

// just a quick dirty conversion
let obj = contacts.reduce((a, c) => (a[c.id] = c, a), {})

//Object looks like:
console.log(obj)

// find the largest key // maybe a good way to decide the next key
largest_id = Math.max(...Object.keys(obj))
console.log("largest ID", largest_id)

// is ID 4 taken?
console.log("is there a 4", 4 in obj) //yes
// alternatively obj.hasOwnProperty('4')

// is 5?
console.log("is there a 5", 5 in obj) //no

// update ID 4:
obj['4'].first = "Mark"
console.log(obj['4'])

希望这是尝试这种方法而不是数组的一点动力。