how to get repeated values from an array of objects in JavaScript?

Question

my issue is that I need to filter a set of data...

my data carries..

var arrayWithDuplicates = [
    {"licenseNum": "6", "state":"NV"},
    {"licenseNum": "6", "state":"NV"},
    {"licenseNum": "6", "state":"NV"},
    {"licenseNum": "6", "state":"CA"},
    {"licenseNum": "6", "state":"CA"},
    {"licenseNum": "6", "state":"OR"},
    {"licenseNum": "6", "state":"OR"},
    {"licenseNum": "6", "state":"OR"},
    {"licenseNum": "20", "state":"NV"},
    {"licenseNum": "10", "state":"CA"},
    {"licenseNum": "10", "state":"NV"},
    {"licenseNum": "10", "state":"OR"},
    {"licenseNum": "10", "state":"CA"}
];

new data should be

newdata = [6, 6, 6, 20, 10, 10, 10];

I've tried to do..

for (i = 0; i < arrayWithDuplicates .length; i++) {
                if ((arrayWithDuplicates[i].licenseNum) === -1)) {
                    newdata .push({
                        licenseNum: arrayWithDuplicates[i].licenseNum,
                        state: arrayWithDuplicates[i].state
                    });
                }
            };

the result from what these, I get..

newdata = [6, 20, 10]

I've seen a lot of great examples, but it still doesn't resolve my issue. much appreciated.

What are the examples you're referring to and why didn't they work? — Patrick Roberts
– Patrick Roberts, Commented Jun 22, 2018 at 17:29
@PatrickRoberts, this is the example that I thought it was close to what I am looking for..stackoverflow.com/questions/2218999/… — tieguanyindev
– tieguanyindev, Commented Jun 22, 2018 at 17:34
Rather than pointing us to things you think are what you want, tell us what you want. You've given us a before and after, with no information about the parts inbetween. — Taplar
– Taplar, Commented Jun 22, 2018 at 17:35

kiddorails · Accepted Answer · 2018-06-22 17:43:49Z

3

Get unique entries and filter out what you need. Find comments inline below to see the approach

var arrayWithDuplicates = [
    {"licenseNum": "6", state:"NV"},
    {"licenseNum": "6", state:"CA"},
    {"licenseNum": "6", state:"OR"},
    {"licenseNum": "6", state:"OR"},
    {"licenseNum": "6", state:"OR"},
    {"licenseNum": "20", state:"NV"},
    {"licenseNum": "10", state:"CA"},
    {"licenseNum": "10", state:"CA"},
    {"licenseNum": "10", state:"OR"},
    {"licenseNum": "10", state:"CA"}
];

json = arrayWithDuplicates.map(x => JSON.stringify(x)) // maps each array entry in stringified json, so I could get unique entries below

var result = json.filter(function(item, pos) {
    return json.indexOf(item) == pos; // gives unique entries
}).map(x => +JSON.parse(x).licenseNum) // parses back json and gives licenseNum
console.log(result)
// [6, 6, 6, 20, 10, 10]

edited Jun 22, 2018 at 17:43

answered Jun 22, 2018 at 17:35

kiddorails

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1 Comment

kiddorails Over a year ago

@formosanblackbear that's great. you can accept this as answer if it helped you out. And will urge you to be more specific with your queries in future; it saves a lot of time for everyone :)

Tom G · Accepted Answer · 2018-06-22 17:45:20Z

1

var arrayWithDuplicates = [
    {"licenseNum": "6", state:"NV"},
    {"licenseNum": "6", state:"CA"},
    {"licenseNum": "6", state:"OR"},
    {"licenseNum": "6", state:"OR"},
    {"licenseNum": "6", state:"OR"},
    {"licenseNum": "20", state:"NV"},
    {"licenseNum": "10", state:"CA"},
    {"licenseNum": "10", state:"CA"},
    {"licenseNum": "10", state:"OR"},
    {"licenseNum": "10", state:"CA"}
];

var newdata = [];
var seens = [];
for(var i = 0; i < arrayWithDuplicates.length; i++) {
  var obj = arrayWithDuplicates[i];
  var lookupKey = obj.licenseNum + "|" + obj.state;
  if(seens.indexOf(lookupKey) == -1) {
    newdata.push(obj.licenseNum);
    seens.push(lookupKey);
  }
}

console.log(newdata);

answered Jun 22, 2018 at 17:45

Tom G

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3 Comments

tieguanyindev Over a year ago

sweet! this helped.

Tom G Over a year ago

Glad it worked for you formosanblackbear, happy coding!

kiddorails Over a year ago

adding the information about what code is doing is often advisable.

JackNavaRow · Accepted Answer · 2018-06-22 18:09:46Z

1

a small change proposed by @kiddorails in an unique function

var arrayWithDuplicates = [
    {"licenseNum": "6", state:"NV"},
    {"licenseNum": "6", state:"CA"},
    {"licenseNum": "6", state:"OR"},
    {"licenseNum": "6", state:"OR"},
    {"licenseNum": "6", state:"OR"},
    {"licenseNum": "20", state:"NV"},
    {"licenseNum": "10", state:"CA"},
    {"licenseNum": "10", state:"CA"},
    {"licenseNum": "10", state:"OR"},
    {"licenseNum": "10", state:"CA"}
];

json = arrayWithDuplicates.map(x => JSON.stringify(x)) 
let result = [];
json.forEach(function(item, pos) {
    if (json.indexOf(item) == pos) {
      result.push(+JSON.parse(item).licenseNum)
    }
})
console.log(result)

edited Jun 22, 2018 at 18:09

answered Jun 22, 2018 at 18:08

JackNavaRow

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1 Comment

kiddorails Over a year ago

you may want to result.push(+JSON.parse(item).licenseNum)

JackNavaRow · Accepted Answer · 2018-06-22 18:35:44Z

1

ES6 JS:

var arr = [
    {"licenseNum": "6", state:"NV"},
    {"licenseNum": "6", state:"CA"},
    {"licenseNum": "6", state:"OR"},
    {"licenseNum": "20", state:"NV"},
    {"licenseNum": "10", state:"CA"},
    {"licenseNum": "10", state:"OR"}
];

var newarr = arr.
    filter((x, i) => arr.some((y, j) => {
        return y.licenseNum == x.licenseNum && i != j
    }))
    .map(x => x.licenseNum)
    console.log(newarr)

edited Jun 22, 2018 at 18:35

JackNavaRow

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answered Jun 22, 2018 at 17:48

user2693928

3 Comments

Ivan Over a year ago

you could've used const just as another ES6 signature ;)

Ivan Over a year ago

However the result here isn't [6, 6, 6, 20, 10, 10, 10]

user2693928 Over a year ago

Try this var newarr = arr. reduce((acc, x, i) => { const gr = x.licenseNum + x.state; if ( ! acc.groups[gr]) { acc.res.push(x.licenseNum); acc.groups[gr] = 1 } return acc }, {groups: [], res: []}).res

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