[javascript] Remove Duplicate objects from JSON Array

I have an array that looks like this:

var standardsList = [
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Geometry"},
    {"Grade": "Math 1", "Domain": "Counting & Cardinality"},
    {"Grade": "Math 1", "Domain": "Counting & Cardinality"},
    {"Grade": "Math 1", "Domain": "Orders of Operation"},
    {"Grade": "Math 2", "Domain": "Geometry"},
    {"Grade": "Math 2", "Domain": "Geometry"}
];

And I need to remove the duplicates so that something like this remains:

var standardsList = [
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Geometry"},
    {"Grade": "Math 1", "Domain": "Counting & Cardinality"},
    {"Grade": "Math 1", "Domain": "Orders of Operation"},
    {"Grade": "Math 2", "Domain": "Geometry"}
];

I've tried installing underscore.js and using ._uniq but that only seems to work when a single key:value pair appears in the object. I can't seem to get it to work across multiple keys.

When I try something like:

var uniqueStandards = _.uniq(standardsList, function(item, key, Domain){
    return item.Domain;
});

I only get the first three unique values (one per grade). But I need all the unique values across both grade and domain. Is there a simple way to feed both keys to the _.uniq function?

Ultimately, I need a list with the each unique grade as the header and the unique domains as the list items to pass into an HTML page. I may be going about this wrong, so if there is an easier way to accomplish that end goal, I am open to ideas.

Thanks in advance!

Edit: Getting some good responses and wanted to clarify what my end goal was. I'm trying to create a series of lists in HTML of the form:

<div>
    <h3>Math K</h3>
    <li>Counting & Cardinality</li>
    <li>Geometry</li>
</div>
<div>
    <h3>Math 1</h3>
    <li>Counting & Cardinality</li>
    <li>Orders of Operation</li>
</div>
<div>
    <h3>Math 2</h3>
    <li>Geometry</li>
</div>

My original though was to create an array and push that into the <div> element on the page with $("#divid").append(array)

Use this Pseudocode

var standardsList = [
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Geometry"},
    {"Grade": "Math 1", "Domain": "Counting & Cardinality"},
    {"Grade": "Math 1", "Domain": "Counting & Cardinality"},
    {"Grade": "Math 1", "Domain": "Orders of Operation"},
    {"Grade": "Math 2", "Domain": "Geometry"},
    {"Grade": "Math 2", "Domain": "Geometry"}
];
var newArr =[]
for(var i in standardsList){
    newArr.push(JSON.stringify(standardsList[i]))
}
var obj = {};
newArr= newArr.filter((item)=>{
    return obj.hasOwnProperty(item) ? false : (obj[item] = true);
})
standardsList.length = 0
for(var i in newArr){
    standardsList.push(JSON.parse(newArr[i]))
}
console.log(standardsList)

I have choose a sample array similar to yours. Its easier to compare objects once you stringfy them. Then you just have to compare strings.

The following works for me:

_.uniq(standardsList, JSON.stringify)

This would probably be slow for very long lists, however.

function arrUnique(arr) {
    var cleaned = [];
    arr.forEach(function(itm) {
        var unique = true;
        cleaned.forEach(function(itm2) {
            if (_.isEqual(itm, itm2)) unique = false;
        });
        if (unique)  cleaned.push(itm);
    });
    return cleaned;
}

var standardsList = arrUnique(standardsList);

FIDDLE

This will return

var standardsList = [
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Geometry"},
    {"Grade": "Math 1", "Domain": "Counting & Cardinality"},
    {"Grade": "Math 1", "Domain": "Orders of Operation"},
    {"Grade": "Math 2", "Domain": "Geometry"}
];

Which is exactly what you asked for ?

You can use lodash, download here (4.17.15)

Example code:

var object = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }, { 'x': 1, 'y': 2 }];

_.uniqWith(object, _.isEqual);

// => [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }]

Reviving an old question, but I wanted to post an iteration on @adeneo's answer. That answer is completely general, but for this use case it could be more efficient (it's slow on my machine with an array of a few thousand objects). If you know the specific properties of the objects you need to compare, just compare them directly:

var sl = standardsList;
var out = [];

for (var i = 0, l = sl.length; i < l; i++) {
    var unique = true;
    for (var j = 0, k = out.length; j < k; j++) {
        if ((sl[i].Grade === out[j].Grade) && (sl[i].Domain === out[j].Domain)) {
            unique = false;
        }
    }
    if (unique) {
        out.push(sl[i]);
    }
}

console.log(sl.length); // 10
console.log(out.length); // 5

I needed to do some de-duping of JSON objects so I stumbled across this page. However, I went with the short ES6 solution (no need for external libs), running this in Chrome Dev Tools Snippets:

const data = [ /* any list of objects */ ];
const set = new Set(data.map(item => JSON.stringify(item)));
const dedup = [...set].map(item => JSON.parse(item));
console.log(`Removed ${data.length - dedup.length} elements`);
console.log(dedup);

I know there are many answers already but the best one that worked for me for a complex json structure is:

var arr = [{ "State": "RWCW", "desc": "WEST", "code": "RWCW", "level": 0, "save": "RWCW : WEST", "attribute1": "", "attribute2": "" }, { "State": "RSCW", "desc": "SOUTHEAST", "code": "RSCW", "level": 0, "save": "RSCW : SOUTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RCSW", "desc": "SOUTHWEST", "code": "RCSW", "level": 0, "save": "RCSW : SOUTHWEST", "attribute1": "", "attribute2": "" }, { "State": "RECW", "desc": "NORTHEAST", "code": "RECW", "level": 0, "save": "RECW : NORTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RWCW", "desc": "WEST", "code": "RWCW", "level": 0, "save": "RWCW : WEST", "attribute1": "", "attribute2": "" }, { "State": "RWCW", "desc": "WEST", "code": "RWCW", "level": 0, "save": "RWCW : WEST", "attribute1": "", "attribute2": "" }, { "State": "RSCW", "desc": "SOUTHEAST", "code": "RSCW", "level": 0, "save": "RSCW : SOUTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RCSW", "desc": "SOUTHWEST", "code": "RCSW", "level": 0, "save": "RCSW : SOUTHWEST", "attribute1": "", "attribute2": "" }, { "State": "RECW", "desc": "NORTHEAST", "code": "RECW", "level": 0, "save": "RECW : NORTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RWCW", "desc": "WEST", "code": "RWCW", "level": 0, "save": "RWCW : WEST", "attribute1": "", "attribute2": "" }, { "State": "RSCW", "desc": "SOUTHEAST", "code": "RSCW", "level": 0, "save": "RSCW : SOUTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RECW", "desc": "NORTHEAST", "code": "RECW", "level": 0, "save": "RECW : NORTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RWCW", "desc": "WEST", "code": "RWCW", "level": 0, "save": "RWCW : WEST", "attribute1": "", "attribute2": "" }, { "State": "RCSW", "desc": "SOUTHWEST", "code": "RCSW", "level": 0, "save": "RCSW : SOUTHWEST", "attribute1": "", "attribute2": "" }, { "State": "RWCW", "desc": "WEST", "code": "RWCW", "level": 0, "save": "RWCW : WEST", "attribute1": "", "attribute2": "" }, { "State": "RCNW", "desc": "MIDWEST", "code": "RCNW", "level": 0, "save": "RCNW : MIDWEST", "attribute1": "", "attribute2": "" }, { "State": "RCSW", "desc": "SOUTHWEST", "code": "RCSW", "level": 0, "save": "RCSW : SOUTHWEST", "attribute1": "", "attribute2": "" }, { "State": "RECW", "desc": "NORTHEAST", "code": "RECW", "level": 0, "save": "RECW : NORTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RCNW", "desc": "MIDWEST", "code": "RCNW", "level": 0, "save": "RCNW : MIDWEST", "attribute1": "", "attribute2": "" }, { "State": "RSCW", "desc": "SOUTHEAST", "code": "RSCW", "level": 0, "save": "RSCW : SOUTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RECW", "desc": "NORTHEAST", "code": "RECW", "level": 0, "save": "RECW : NORTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RCNW", "desc": "MIDWEST", "code": "RCNW", "level": 0, "save": "RCNW : MIDWEST", "attribute1": "", "attribute2": "" }, { "State": "RSCW", "desc": "SOUTHEAST", "code": "RSCW", "level": 0, "save": "RSCW : SOUTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RSCW", "desc": "SOUTHEAST", "code": "RSCW", "level": 0, "save": "RSCW : SOUTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RSCW", "desc": "SOUTHEAST", "code": "RSCW", "level": 0, "save": "RSCW : SOUTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RCNW", "desc": "MIDWEST", "code": "RCNW", "level": 0, "save": "RCNW : MIDWEST", "attribute1": "", "attribute2": "" }, { "State": "RSCW", "desc": "SOUTHEAST", "code": "RSCW", "level": 0, "save": "RSCW : SOUTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RECW", "desc": "NORTHEAST", "code": "RECW", "level": 0, "save": "RECW : NORTHEAST", "attribute1": "", "attribute2": "" }];_x000D_
_x000D_
var clean = arr.filter((arr, index, self) =>_x000D_
    index === self.findIndex((t) => (t.save === arr.save && t.State === arr.State)))_x000D_
_x000D_
console.log(clean);

You can try this directly to chrome browser console and edit according to your need.

I hope this helps someone.

**The following method does the way you want. It filters the array based on all properties values. **

    var standardsList = [
  { "Grade": "Math K", "Domain": "Counting & Cardinality" },
  { "Grade": "Math K", "Domain": "Counting & Cardinality" },
  { "Grade": "Math K", "Domain": "Counting & Cardinality" },
  { "Grade": "Math K", "Domain": "Counting & Cardinality" },
  { "Grade": "Math K", "Domain": "Geometry" },
  { "Grade": "Math 1", "Domain": "Counting & Cardinality" },
  { "Grade": "Math 1", "Domain": "Counting & Cardinality" },
  { "Grade": "Math 1", "Domain": "Orders of Operation" },
  { "Grade": "Math 2", "Domain": "Geometry" },
  { "Grade": "Math 2", "Domain": "Geometry" }
];

const removeDupliactes = (values) => {
  let concatArray = values.map(eachValue => {
    return Object.values(eachValue).join('')
  })
  let filterValues = values.filter((value, index) => {
    return concatArray.indexOf(concatArray[index]) === index

  })
  return filterValues
}
removeDupliactes(standardsList) 

Results this

[{Grade: "Math K", Domain: "Counting & Cardinality"}

{Grade: "Math K", Domain: "Geometry"}

{Grade: "Math 1", Domain: "Counting & Cardinality"}

{Grade: "Math 1", Domain: "Orders of Operation"}

{Grade: "Math 2", Domain: "Geometry"}] 

Use Map to remove the duplicates. (For new readers)

var standardsList = [
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Geometry"},
    {"Grade": "Math 1", "Domain": "Counting & Cardinality"},
    {"Grade": "Math 1", "Domain": "Counting & Cardinality"},
    {"Grade": "Math 1", "Domain": "Orders of Operation"},
    {"Grade": "Math 2", "Domain": "Geometry"},
    {"Grade": "Math 2", "Domain": "Geometry"}
];

var grades = new Map();
standardsList.forEach( function( item ) {
    grades.set(JSON.stringify(item), item);
});

console.log( [...grades.values()]);

/*
[
  { Grade: 'Math K', Domain: 'Counting & Cardinality' },
  { Grade: 'Math K', Domain: 'Geometry' },
  { Grade: 'Math 1', Domain: 'Counting & Cardinality' },
  { Grade: 'Math 1', Domain: 'Orders of Operation' },
  { Grade: 'Math 2', Domain: 'Geometry' }
]
*/

Javascript solution for your case:

console.log(unique(standardsList));

function unique(obj){
    var uniques=[];
    var stringify={};
    for(var i=0;i<obj.length;i++){
       var keys=Object.keys(obj[i]);
       keys.sort(function(a,b) {return a-b});
       var str='';
        for(var j=0;j<keys.length;j++){
           str+= JSON.stringify(keys[j]);
           str+= JSON.stringify(obj[i][keys[j]]);
        }
        if(!stringify.hasOwnProperty(str)){
            uniques.push(obj[i]);
            stringify[str]=true;
        }
    }
    return uniques;
}

var standardsList = [_x000D_
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},_x000D_
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},_x000D_
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},_x000D_
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},_x000D_
    {"Grade": "Math K", "Domain": "Geometry"},_x000D_
    {"Grade": "Math 1", "Domain": "Counting & Cardinality"},_x000D_
    {"Grade": "Math 1", "Domain": "Counting & Cardinality"},_x000D_
    {"Grade": "Math 1", "Domain": "Orders of Operation"},_x000D_
    {"Grade": "Math 2", "Domain": "Geometry"},_x000D_
    {"Grade": "Math 2", "Domain": "Geometry"}_x000D_
];_x000D_
_x000D_
standardsList = standardsList.filter((li, idx, self) => self.map(itm => itm.Grade+itm.Domain).indexOf(li.Grade+li.Domain) === idx)_x000D_
_x000D_
document.write(JSON.stringify(standardsList))

here is a functional way of doing it that is much easier

standardsList = standardsList.filter((li, idx, self) => self.map(itm => iem.Grade+itm.domain).indexOf(li.Grade+li.domain) === idx)

var standardsList = [
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Geometry"},
    {"Grade": "Math 1", "Domain": "Counting & Cardinality"},
    {"Grade": "Math 1", "Domain": "Counting & Cardinality"},
    {"Grade": "Math 1", "Domain": "Orders of Operation"},
    {"Grade": "Math 2", "Domain": "Geometry"},
    {"Grade": "Math 2", "Domain": "Geometry"}
];          

 function uniqurArray(array){
                         var a = array.concat();
                        for(var i=0; i<a.length; i++) {
                            for(var j=i+1; j<a.length; j++) {
                                if(a[i].Grade === a[j].Grade){
                                    a.splice(j--, 1);
                                }
                            }
                        }

                        return a;
                    }

    uniqurArray(standardsList) // put this js in console and you get uniq object in array

Here's a short one-liner with es6!

const nums = [
  "AC8818E1",
  "AC8818E1",
  "AC8818E1",
  "AC8818E1",
  "AC8818E1",
  "AC9233F2015",
  "AC9233F2015",
  "AC9233F2015",
  "AC8818E1",
  "AC8818E1",
  "AC8818E1",
  "AC8818E1",
  "AC8818E1",
  "AC8818E2",
  "AC8818E2",
  "AC8818E2",
  "AC8818E2",
  "AC9233F2015",
  "AC9233F2015",
  "AC9233F2015",
  "AC9233F2015",
  "AC8818E1",
  "AC8818E1",
  "AC8818E1",
  "AC8818E2",
  "AC8818E2",
  "AC9233F2015",
  "AC9233F2015",
  "AC8818E1",
  "AC8818E1",
  "AC8818E1",
  "AC8818E2",
  "AC8818E2",
  "AC8818E2",
  "AC8818E2",
  "ACB098F25",
  "ACB098F25",
  "ACB098F25",
  "ACB098F25",
  "AC8818E2",
  "AC8818E2",
  "AC8818E1",
  "AC8818E1",
  "AC8818E1",
  ]

Set is a new data object introduced in ES6. Because Set only lets you store unique values. When you pass in an array, it will remove any duplicate values.

export const $uniquenums = [...new Set(nums)].sort();