CODEWITHSUNDEEP
javascriptnode.js
Lion Smith
Lion Smith

Reputation: 655

get last id number on json array javascript

i have a sample json array that contains a list of employeeId's

[{"employeeId": "20180000002"},{"employeeId": "20180000001"},{"employeeId":"20180000003"},{"employeeId": "20180000000"}]

wanted to get the last id which is employeeId":"20180000003 

$.ajax({
    url:'api/applicants/getwatchers',
    type:'GET',
    success: function(data){
        watcherId = (data[data.length-1].employeeId || watcherId);
        newWatcherId = parseInt(watcherId) + 1;
        console.log(watcherId);

    }
});

but the console.log was employeeId": "20180000000

Upvotes: 0

Views: 1357

Answers (4)

void
void

Reputation: 36703

Use Math.max() on the array of employeeId using the spread operator.

var maxId = Math.max(...data.map(el=>el. employeeId)); // Will give you the max ID
watcherId = (maxId || watcherId);
newWatcherId = parseInt(watcherId) + 1;
console.log(watcherId);

Upvotes: 0

gurvinder372
gurvinder372

Reputation: 68393

wanted to get the last id which is employeeId":"20180000003

By last id, if you meant largest id (generated last by the system), then use Math.max.apply and map

var arr = [{"employeeId": "20180000002"},{"employeeId": "20180000001"},{"employeeId":"20180000003"},{"employeeId": "20180000000"}];
watcherId = Math.max.apply( null, arr.map( s => +s.employeeId ) );

watcherId is already a Number, no need to do parseInt, so the newWatcherId becomes

newWatcherId = watcherId  + 1;

Upvotes: 3

Bibek Shah
Bibek Shah

Reputation: 429

You can sort the array in descending order and then get the first one as shown below:

list = [{"employeeId": "20180000002"},{"employeeId": "20180000001"},{"employeeId":"20180000003"},{"employeeId": "20180000000"}];
sortedIds = list.map(emp => emp.employeeId) // map the array to empIds.
    .sort((a, b) => b - a)[0];              // sort desc.
lastId = sortedIds[0];

Upvotes: 0

Lucas Tétreault
Lucas Tétreault

Reputation: 953

You need to sort the array before you grab the last element if you want to get the largest number.

$.ajax({
url:'api/applicants/getwatchers',
type:'GET',
success: function(data){
    data.sort((a,b) => b.employeeId - a.employeeId)
    watcherId = (data[data.length-1].employeeId || watcherId);
    newWatcherId = parseInt(watcherId) + 1;
    console.log(watcherId);

}
});

It's possible I got the sort backwards - I always do that haha. In which case try: 

data.sort((a,b) => a.employeeId - b.employeeId)

Upvotes: 0

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