Get last obj value of same type in json using jquery

Question

I have JSON Data and i need last obj value from same type obj values.

I want to Get last index of Foo value Bar.

I know how to get last index of json array.

var data = [{
    "foo": "bar"
  },
  {
    "foo": "bar-1"
  },
  {
    "foo": "bar-2"
  },
  {
    "foo": "bar-1"
  },
  {
    "foo": "bar"
  },
  {
    "foo": "bar-1"
  },

]



$.each(data, function(key, val) {
  if (val.foo == "bar") {
    console.log(key);
  }
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

@mplungjan Then perhaps, instead of answering the question, you can help find the duplicate. Because there is one. — Heretic Monkey, Mar 03 '17 at 15:00
@MikeMcCaughan - that took longer than to write an answer :) — mplungjan, Mar 03 '17 at 15:02
@anuj, what do you need to do next, since you believe you need jQuery? — mplungjan, Mar 03 '17 at 15:07

mplungjan · Answer 1 · 2017-03-03T15:56:41.670

2

No need for jQuery, just loop in reverse:

Assuming the element you want IS near the end. If not, then any of the reduce or map answers given will likely not be much slower

var data = [
  {"foo": "bar"},
  {"foo": "bar-1"},
  {"foo": "bar-2"},
  {"foo": "bar-1"},
  {"foo": "bar"},
  {"foo": "bar-1"} // no comma on the last
]


// Find the last `bar`

for (var i=data.length-1;i>=0;i--) {
  if (data[i].foo == "bar") {
    console.log('Last of Foo Bar is ' +i);
    break;
  }
}

// Find the last `bar` AND the last bar-1
var bars = { "bar":-1, "bar-1":-1, "done":0 }, numBars = 2;
for (var i=data.length-1;bars["done"]<numBars && i>=0;i--) {
  if (bars[data[i].foo]==-1) {
    bars[data[i].foo] = i;
    bars["done"]++;
  }
}
console.log(JSON.stringify(bars));

edited Mar 03 '17 at 15:56

answered Mar 03 '17 at 14:53

mplungjan

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but i need jquery each loop as i need to do further work.. btw thanks for solution :) – anuj khandelwal Mar 03 '17 at 14:59
1

Using `$.each` makes no difference - you're looping over an array of objects. jQuery is irrelevant, and in this case, more redundant. – Rory McCrossan Mar 03 '17 at 15:00
1

This is the most efficient answer, I've removed mine to reduce noise. Too much overthinking from me. :) – Ian Stanley Mar 03 '17 at 15:04
@IanStanley however your solution was the best of the non-efficient ones ;) – mplungjan Mar 03 '17 at 15:05
@IanStanley I also now realise that if the element wanted is the first or near the beginning, then your code will likely not be much slower – mplungjan Mar 03 '17 at 15:16
@mplungjan in case if i need to find bar and bar-1 then what should i need to do? – anuj khandelwal Mar 03 '17 at 15:44
See update............. – mplungjan Mar 03 '17 at 15:56

score 2 · Answer 2 · answered Mar 03 '17 at 14:55

2

You could just use reduce() and when element is found set accumulator value to index of that element. So then index of last element found will be returned.

var data = [{"foo":"bar"},{"foo":"bar-1"},{"foo":"bar-2"},{"foo":"bar-1"},{"foo":"bar"},{"foo":"bar-1"}]

var lastIndex = data.reduce(function(r, e, i) {
  if(e.foo == 'bar') r = i
  return r;
}, null)

console.log(lastIndex)

answered Mar 03 '17 at 14:55

Nenad Vracar

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This will also take longer than just reverse looping – mplungjan Mar 03 '17 at 15:02
@mplungjan Yes, your solution is more efficient for this specific task, but maybe op need to loop all elements for some reason. – Nenad Vracar Mar 03 '17 at 15:05
He says he does need jQuery for some reason. I would like to know what else he wants to do – mplungjan Mar 03 '17 at 15:06
Also if the last bar is near the beginning, my code will also have to look at them all – mplungjan Mar 03 '17 at 15:20

score 1 · Answer 3 · answered Mar 03 '17 at 14:55

1

Actually you don't need to use jQuery to solve it.

var data = [{foo:"bar"},{foo:"bar-1"},{foo:"bar-2"},{foo:"bar-1"},{foo:"bar"},{foo:"bar-1"}],
    indexes = [];
    data.forEach((v,i) => v.foo == 'bar' ? indexes.push(i) : v);

console.log(`Index of last 'bar' key is ${indexes[indexes.length-1]}`);

answered Mar 03 '17 at 14:55

kind user

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Again that will take much longer than just reverse looping – mplungjan Mar 03 '17 at 14:58
@mplungjan *Much longer*. Oh, please. – kind user Mar 03 '17 at 15:07
Of course with the array in OP's example it does not matter, However we have no way of knowing how big the actual array is. Never assume that the example matches reality. You could be creating thousands of items just to find the last of the ones your pushed. – mplungjan Mar 03 '17 at 15:10
@mplungjan I just mean that it would be perceptible only for very huge arrays. In this particular case, it doesn't really matter. But I also agree with you, we can't just assume that OP won't use it for bigger variables. (: – kind user Mar 03 '17 at 15:12

Get last obj value of same type in json using jquery

3 Answers3