AJAX JSON响应返回正确的值，但两者之间是否还有未定义的值？

Question

I'm working on some JavaScript code that is going to find the smallest unused number in a specified range of numbers. The AJAX request gathers all used numbers in the specified range, but is additionally returning undefined values in between the correct values? I've compared the returned values from the JSON response to what's currently in the SQL table and all the correct values are in both the JSON response and the SQL table, so I'm not sure where the undefined values are coming from.

https://imgur.com/a/rXLfEJk

JavaScript:

//Specified range of numbers to search.
var startRange = 40000;
var endRange = 49999;

//UPC's are padded with to 13 digits with 0's then sent as parameters.
var startUPC = '00000000' + startRange;
var endUPC = '00000000' + endRange;

// AJAX call to web API that gathers all UPC's within a range.
$.ajax({
    url: "api/GetNewPLU",
    type: "GET",
    dataType: "json",
    data: { 'startUPC': startUPC, 'endUPC': endUPC },
    success: function (data) {
        $.each(data.data, function (i, UPCs) {
            for (var i in UPCs) {
                console.log("UPC: " + UPCs[i].F01);
            }
        })
    },
    error: function (error) {
        console.log(`Error ${error}`)
    }
})

JSON Response:

{
    "draw": null,
    "data": [{
        "DT_RowId": "row_0000000040002",
        "OBJ_TAB": {
            "F01": "0000000040002"
        }
    }, {
        "DT_RowId": "row_0000000040008",
        "OBJ_TAB": {
            "F01": "0000000040008"
        }
    }, {
        "DT_RowId": "row_0000000040013",
        "OBJ_TAB": {
            "F01": "0000000040013"
        }
    }, {
        "DT_RowId": "row_0000000040017",
        "OBJ_TAB": {
            "F01": "0000000040017"
        }
    }
}

I plan to loop through the used numbers from the AJAX request comparing them to a sequentially incremented generated number until there is not a match and then save that unused number. I'm not sure if it's worth figuring out why I'm returning both values and undefined or if I should just find a way to filter out the undefined.

Answer 1

lodash _.difference can help to you.
Create two arrays. One for generated values, one for used values. And find diff between them.

var created = ["0000000040000", "0000000040001", "0000000040002"];
var used = ["0000000040001", "0000000040002"];
var unused = _.difference(created, used);