angularjs: check if value exists in array of objects - javascript

var a = [ { id:1}, {id:2} ];
var b = {id:1};
var res = a.indexOf(b._id) == -1;
console.log(res);
I want to check if b._id is in a[].
Note: a[] is an array of objects


Try this..
var a = [{ id:1}, {id:2}];
var b={id:1};
var arrayWithIds = a.map(function(x){
return x.id
}); // get new array contains all ids
var present = arrayWithIds.indexOf(b.id) != -1 // find the b.id array
console.log(present);
Here is the reference for Map and indexOf


This should work :
var a = [ { id:1} ,{id:2} ];
var b={id:1}
console.log(a.findIndex(function(obj){return obj.id=b.id}))
indexOf works when you are dealing with indexed arrays not with array of objects.


Please use the following code:
var a = [ { id:1}, {id:2} ];
var b={id:1}
function findMatch(element) {
return element.id === b.id;
}
console.log(a.findIndex(findMatch));


A better way is using .find function.
let a = [{
id: 1
}, {
id: 2
}],
b = {
id: 1
},
obj = a.find(function(itm) {
return itm.id == b.id;
});
console.log(obj)
And also using .findIndex function to get just index of item in array.
let a = [{
id: 1
}, {
id: 2
}],
b = {
id: 1
},
objIndex = a.findIndex(function(itm) {
return itm.id == b.id;
});
console.log(objIndex)
And for getting all objects with that condition use .filter function.
let a = [{
id: 1
}, {
id: 2
}],
b = {
id: 1
},
objArr = a.filter(function(itm) {
return itm.id == b.id;
});
console.log(objArr)


Array.map() function compare id and its value and return a Boolean value if map as commented by #Slava Utesinov
var a = [{id: 1}, {id: 2}];
var b = {id: 1};
if(a.map(x => x.id).indexOf(b.id) != -1){
console.log("Exists");
}else{
console.log("Not exists");
}


try this
var a = [ { id:1} ,{id:2} ];
var b={id:1}
console.log(a.find(x=>x.id==b.id))// return matched record
var a = [ { id:1} ,{id:2} ];
var b={id:3}
console.log(a.find(x=>x.id==b.id)) //return undefined


Use Array.map() function of JavaScript to check it. It will compare id and its value as well.
Below is working code:
var a = [{
id: 1
}, {
id: 2
}];
var b = {
id: 1
};
if (a.map(x => x.id).indexOf(b.id) != -1) {
console.log("Available");
} else {
console.log("Not available");
}


You can use Filter of AngularJS
var a = [{id:1}, {id:2}];
var b = {id:1};
var found = false;
var filterResult = $filter('filter')(a, {id: b.id}, true);
if (filterResult.length > 0) {
found = true;
}

Related

Perform .join on a complex object with array of object dynamically

I have a complex js object, that contains arrays of an object. The problem is some of the main object properties' arrays can have a different property.
var foo = {};
foo.prop1 = [
{name:"test", skill:1},
{name:"test2", skill:2},
];
foo.prop2 = [
{address:"Earth",distance:1},
{address:"Mars", distance:2}
]
My aim is to just replace the main object property value with the joined values for retrieval.
This is what I have right now.
if(Object.keys(foo).length){
Object.keys(foo).forEach(key => {
var x = foo[key];
if(key === "address") {
foo[key] = x.map(function(elem){return elem.address;}).join(";");
} else {
foo[key] = x.map(function(elem){return elem.name;}).join(";");
}
});
}
How can I make it dynamic so that I don't need to use the if statement? I just want to join all the first property of the inner obj.
Result:
foo new values would be:
foo.prop1 = test;test2
foo.prop2 = Earth;Mars
I got it. I just want to join the first property of the sub object.
I replaced the if with this
foo[key] = x.map(function(elem){return elem[Object.keys(elem)[0]]; }).join(";");

I guess you are trying to choose the value with string type
var foo = {};
foo.prop1 = [{
name: "test",
skill: 1
},
{
name: "test2",
skill: 2
},
];
foo.prop2 = [{
address: "Earth",
distance: 1
},
{
address: "Mars",
distance: 2
}
]
function formulate() {
const result = {};
(Object.keys(foo) || []).forEach(function(k) {
result[k] = foo[k].map(function(val) {
str_key = Object.keys(val).filter(function(val_k) {
return typeof val[val_k] === "string";
});
return str_key.map(function(s) {
return val[s];
});
}).join(";");
});
return result;
}
result = formulate()
console.log(result);

I hope, this will work for you
var foo = {};
foo.prop1 = [
{name:"test", skill:1},
{name:"test2", skill:2},
];
foo.prop2 = [
{address:"Earth",distance:1},
{address:"Mars", distance:2}
]
Object.keys(foo).forEach(key => {
foo[key]=foo[key].map(val => { return Object.entries(val)[0][1] } ).toString().split(",").join(";")
});
console.log(foo)

Merge array with underscore by keys

I have 2 arrays :
[{id:1,name:"name"},{id:2,name:"name2"} ,{id:3,name:"name3"}]
[{id:1,date:"123"},{id:2,date:"456"}]
Array 1 should be updated only if the id is equal :
So the array 1 will looks like
It should not create a new array . Only update the array 1 based on array 2
[{id:1,name:"name",date:"123"},{id:2,name:"name2",date:"456"} ,{id:3,name:"name3"}]
I managed to do that with for loop on array2 and inside the for filter like the following :
._filter(array1,function(item){
If(item.id=array2.id)
Do smth and update the array1.date
})
How do I doing that in he best way ? Using underscore.js

You can do something like this:
Iterate over array1 and check if the id of each item exists in array2 by using the some() method.
var arr1 = [{id:1,name:"name"},{id:2,name:"name2"} ,{id:3,name:"name3"}];
var arr2 = [{id:1,date:"123"},{id:2,date:"456"}];
var missing = [];
arr1.forEach( (item1, i) => {
var isExist = arr2.some(item2 => item2.id === item1.id)
if(!isExist) {
missing.push(i);
}
})
missing.forEach(item => {
arr2.push(arr1[item]);
})
console.log(arr2);
reference for some()

Try this :
var a = [{id:1,name:"name"},{id:2,name:"name2"} ,{id:3,name:"name3"}] ;
var b = [{id:1,date:"123"},{id:2,date:"456"}] ;
var i = 0, j = 0 ;
while( i < a.length ) {
j = 0 ;
while( j < b.length) {
if ( a[i].id === b[j].id )
Object.assign( a[i] , b[j] );
j++;
}
i++;
}
console.log(a) ;

You can use forEach to iterate over the second array and use findIndex to get the matched element from first array. If the id matches then update the object in the first array
let arr1 = [{
id: 1,
name: "name"
}, {
id: 2,
name: "name2"
}, {
id: 3,
name: "name3"
}]
let arr2 = [{
id: 1,
date: "123"
}, {
id: 2,
date: "456"
}]
arr2.forEach(function(acc) {
let findArry1Index = arr1.findIndex(function(item) {
return item.id === acc.id;
});
if (findArry1Index !== -1) {
arr1[findArry1Index].date = acc.date;
}
});
console.log(arr1)

You can do it using native language like this:
const arr1 = [{id:1,name:"name"},{id:2,name:"name2"} ,{id:3,name:"name3"}];
const arr2 = [{id:1,date:"123"},{id:2,date:"456"}];
arr1.forEach((ele) => {
const match = arr2.find(item => ele.id === item.id) || {};
Object.assign(ele, match);
});
console.log(arr1);

var a = [{id:1,name:"name"},{id:2,name:"name2"} ,{id:3,name:"name3"}];
var b = [{id:1,date:"123"},{id:2,date:"456"}];
a = _.map(a, function(e) { return _.extend(e, _.findWhere(b, {id: e.id})); });
a results in:
0: {id: 1, name: "name", date: "123"}
1: {id: 2, name: "name2", date: "456"}
2: {id: 3, name: "name3"}
However, I guess this qualifies as "creating a new array"? Maybe it can serve as an inspiration though ¯\_(ツ)_/¯

You can use underscore's indexBy function to index your second array by id, and then simply use Object.assign(...) to update your first array's elements with their corresponding match by performing a lookup in the indexed elements object.
let arr1 = [{id:1, name:"name"}, {id:2, name:"name2"}, {id:3, name:"name3"}]
let arr2 = [{id:1, date:"123"}, {id:2, date:"456"}]
const arr2Groups = _.indexBy(arr2, e => e.id);
arr1.forEach(e => Object.assign(e, arr2Groups[e.id] || {}));
console.log(arr1);
<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.9.1/underscore-min.js"></script>

Find Duplicate Array By Caption without using multiple loops [duplicate]

I need some help with iterating through array, I keep getting stuck or reinventing the wheel.
values = [
{ name: 'someName1' },
{ name: 'someName2' },
{ name: 'someName1' },
{ name: 'someName1' }
]
How could I check if there are two (or more) same name value in array? I do not need a counter, just setting some variable if array values are not unique. Have in mind that array length is dynamic, also array values.

Use array.prototype.map and array.prototype.some:
var values = [
{ name: 'someName1' },
{ name: 'someName2' },
{ name: 'someName4' },
{ name: 'someName2' }
];
var valueArr = values.map(function(item){ return item.name });
var isDuplicate = valueArr.some(function(item, idx){
return valueArr.indexOf(item) != idx
});
console.log(isDuplicate);

ECMA Script 6 Version
If you are in an environment which supports ECMA Script 6's Set, then you can use Array.prototype.some and a Set object, like this
let seen = new Set();
var hasDuplicates = values.some(function(currentObject) {
return seen.size === seen.add(currentObject.name).size;
});
Here, we insert each and every object's name into the Set and we check if the size before and after adding are the same. This works because Set.size returns a number based on unique data (set only adds entries if the data is unique). If/when you have duplicate names, the size won't increase (because the data won't be unique) which means that we would have already seen the current name and it will return true.
ECMA Script 5 Version
If you don't have Set support, then you can use a normal JavaScript object itself, like this
var seen = {};
var hasDuplicates = values.some(function(currentObject) {
if (seen.hasOwnProperty(currentObject.name)) {
// Current name is already seen
return true;
}
// Current name is being seen for the first time
return (seen[currentObject.name] = false);
});
The same can be written succinctly, like this
var seen = {};
var hasDuplicates = values.some(function (currentObject) {
return seen.hasOwnProperty(currentObject.name)
|| (seen[currentObject.name] = false);
});
Note: In both the cases, we use Array.prototype.some because it will short-circuit. The moment it gets a truthy value from the function, it will return true immediately, it will not process rest of the elements.

In TS and ES6 you can create a new Set with the property to be unique and compare it's size to the original array.
const values = [
{ name: 'someName1' },
{ name: 'someName2' },
{ name: 'someName3' },
{ name: 'someName1' }
]
const uniqueValues = new Set(values.map(v => v.name));
if (uniqueValues.size < values.length) {
console.log('duplicates found')
}

To know if simple array has duplicates we can compare first and last indexes of the same value:
The function:
var hasDupsSimple = function(array) {
return array.some(function(value) { // .some will break as soon as duplicate found (no need to itterate over all array)
return array.indexOf(value) !== array.lastIndexOf(value); // comparing first and last indexes of the same value
})
}
Tests:
hasDupsSimple([1,2,3,4,2,7])
// => true
hasDupsSimple([1,2,3,4,8,7])
// => false
hasDupsSimple([1,"hello",3,"bye","hello",7])
// => true
For an array of objects we need to convert the objects values to a simple array first:
Converting array of objects to the simple array with map:
var hasDupsObjects = function(array) {
return array.map(function(value) {
return value.suit + value.rank
}).some(function(value, index, array) {
return array.indexOf(value) !== array.lastIndexOf(value);
})
}
Tests:
var cardHand = [
{ "suit":"spades", "rank":"ten" },
{ "suit":"diamonds", "rank":"ace" },
{ "suit":"hearts", "rank":"ten" },
{ "suit":"clubs", "rank":"two" },
{ "suit":"spades", "rank":"three" },
]
hasDupsObjects(cardHand);
// => false
var cardHand2 = [
{ "suit":"spades", "rank":"ten" },
{ "suit":"diamonds", "rank":"ace" },
{ "suit":"hearts", "rank":"ten" },
{ "suit":"clubs", "rank":"two" },
{ "suit":"spades", "rank":"ten" },
]
hasDupsObjects(cardHand2);
// => true

if you are looking for a boolean, the quickest way would be
var values = [
{ name: 'someName1' },
{ name: 'someName2' },
{ name: 'someName1' },
{ name: 'someName1' }
]
// solution
var hasDuplicate = false;
values.map(v => v.name).sort().sort((a, b) => {
if (a === b) hasDuplicate = true
})
console.log('hasDuplicate', hasDuplicate)

const values = [
{ name: 'someName1' },
{ name: 'someName2' },
{ name: 'someName4' },
{ name: 'someName4' }
];
const foundDuplicateName = values.find((nnn, index) =>{
return values.find((x, ind)=> x.name === nnn.name && index !== ind )
})
console.log(foundDuplicateName)
Found the first one duplicate name
const values = [
{ name: 'someName1' },
{ name: 'someName2' },
{ name: 'someName4' },
{ name: 'someName4' }
];
const foundDuplicateName = values.find((nnn, index) =>{
return values.find((x, ind)=> x.name === nnn.name && index !== ind )
})

You just need one line of code.
var values = [
{ name: 'someName1' },
{ name: 'someName2' },
{ name: 'someName4' },
{ name: 'someName2' }
];
let hasDuplicates = values.map(v => v.name).length > new Set(values.map(v => v.name)).size ? true : false;

Try an simple loop:
var repeat = [], tmp, i = 0;
while(i < values.length){
repeat.indexOf(tmp = values[i++].name) > -1 ? values.pop(i--) : repeat.push(tmp)
}
Demo

With Underscore.js A few ways with Underscore can be done. Here is one of them. Checking if the array is already unique.
function isNameUnique(values){
return _.uniq(values, function(v){ return v.name }).length == values.length
}
With vanilla JavaScript
By checking if there is no recurring names in the array.
function isNameUnique(values){
var names = values.map(function(v){ return v.name });
return !names.some(function(v){
return names.filter(function(w){ return w==v }).length>1
});
}

//checking duplicate elements in an array
var arr=[1,3,4,6,8,9,1,3,4,7];
var hp=new Map();
console.log(arr.sort());
var freq=0;
for(var i=1;i<arr.length;i++){
// console.log(arr[i-1]+" "+arr[i]);
if(arr[i]==arr[i-1]){
freq++;
}
else{
hp.set(arr[i-1],freq+1);
freq=0;
}
}
console.log(hp);

You can use map to return just the name, and then use this forEach trick to check if it exists at least twice:
var areAnyDuplicates = false;
values.map(function(obj) {
return obj.name;
}).forEach(function (element, index, arr) {
if (arr.indexOf(element) !== index) {
areAnyDuplicates = true;
}
});
Fiddle

Adding updated es6 function to check for unique and duplicate values in array. This function is modular and can be reused throughout the code base. Thanks to all the post above.
/* checks for unique keynames in array */
const checkForUnique = (arrToCheck, keyName) => {
/* make set to remove duplicates and compare to */
const uniqueValues = [...new Set(arrToCheck.map(v => v[keyName]))];
if(arrToCheck.length !== uniqueValues.length){
console.log('NOT UNIQUE')
return false
}
return true
}
let arr = [{name:'joshua'},{name:'tony'},{name:'joshua'}]
/* call function with arr and key to check for */
let isUnique = checkForUnique(arr,'name')

checkDuplicate(arr, item) {
const uniqueValues = new Set(arr.map((v) => v[item]));
return uniqueValues.size < arr.length;
},
console.log(this.checkDuplicate(this.dutyExemptionBase, 'CI_ExemptionType')); // true || false

It is quite interesting to work with arrays
You can use new Set() method to find duplicate values!
let's assume you have an array of objects like this...
let myArray = [
{ id: 0, name: "Jhon" },
{ id: 1, name: "sara" },
{ id: 2, name: "pop" },
{ id: 3, name: "sara" }
]
const findUnique = new Set(myArray.map(x => {
return x.name
}))
if(findUnique.size < myArray.length){
console.log("duplicates found!")
}else{
console.log("Done!")
}

const duplicateValues = [{ name: "abc" }, { name: "bcv" }, { name: "abc" }];
const isContainDuplicate = (params) => {
const removedDuplicate = new Set(params.map((el) => el.name));
return params.length !== removedDuplicate.size;
};
const isDuplicate = isContainDuplicate(duplicateValues);
console.log("isDuplicate");

How do i filter array of objects nested in property of array objects?

I have model like this:
var model = [{id: 1, prices: [{count: 2}, {count: 3}]}, {id: 2, prices: [{count: 2}]}, {id: 3, prices: [{count: 3}]}];
and I need to filter this objects of array useing property count and I will need to return matched objects in three scenarios:
if the objects have two objects in array prices,
if the objects have one object in array prices matching count:2,
if the objects have one property in array prices matching count:3.
so..when i click the button without assigned value i wanna see all objects, when i click button with value = 2 i wanna see objects with count: 2 and when i click the button with value = 3 i wanna get objects with count: 3, i must do this in AngularJS –

maybe something like this?
var result = model.filter(function(m) {
// make sure the m.prices field exists and is an array
if (!m.prices || !Array.isArray(m.prices)) {
return false;
}
var numOfPrices = m.prices.length
if (numOfPrices === 2) { // return true if its length is 2
return true;
}
for (var i = 0; i < numOfPrices; i++) {
if (m.prices[i].count &&
(m.prices[i].count === 2 ||
m.prices[i].count == 3)) {
return true;
}
}
return false;
});

use lodash or underscore library.. and then your code with lodash will be like:
_.filter(model, function(i){
return _.intersection(_.map(i.prices, 'count'), [3,2]).length;
})
it returns items that on their price property have array which contains element with count = 3 or count = 2

var model = [{
id: 1,
prices: [{
count: 2
}, {
count: 3
}]
}, {
id: 2,
prices: [{
count: 2
}]
}, {
id: 3,
prices: [{
count: 3
}]
}];
var search = function(data) {
var result = {};
function arrayObjectIndexOf(myArray, searchTerm, property) {
for (var i = 0, len = myArray.length; i < len; i++) {
if (myArray[i][property] === searchTerm) return i;
}
return -1;
}
for (var index in data) {
if (data[index].hasOwnProperty("prices") && arrayObjectIndexOf(data[index].prices, 2, 'count') != -1) {
result[data[index].id] = data[index];
} else if (data[index].hasOwnProperty("prices") && arrayObjectIndexOf(data[index].prices, 3, 'count') != -1) {
result[data[index].id] = data[index];
} else if (data[index].hasOwnProperty("prices") &&
data[index].prices.length == 2) {
result[data[index].id] = data[index];
}
}
return result;
}
var output = search(model);
console.log(output);

How can I check if the array of objects have duplicate property values?

I need some help with iterating through array, I keep getting stuck or reinventing the wheel.
values = [
{ name: 'someName1' },
{ name: 'someName2' },
{ name: 'someName1' },
{ name: 'someName1' }
]
How could I check if there are two (or more) same name value in array? I do not need a counter, just setting some variable if array values are not unique. Have in mind that array length is dynamic, also array values.

Use array.prototype.map and array.prototype.some:
var values = [
{ name: 'someName1' },
{ name: 'someName2' },
{ name: 'someName4' },
{ name: 'someName2' }
];
var valueArr = values.map(function(item){ return item.name });
var isDuplicate = valueArr.some(function(item, idx){
return valueArr.indexOf(item) != idx
});
console.log(isDuplicate);

ECMA Script 6 Version
If you are in an environment which supports ECMA Script 6's Set, then you can use Array.prototype.some and a Set object, like this
let seen = new Set();
var hasDuplicates = values.some(function(currentObject) {
return seen.size === seen.add(currentObject.name).size;
});
Here, we insert each and every object's name into the Set and we check if the size before and after adding are the same. This works because Set.size returns a number based on unique data (set only adds entries if the data is unique). If/when you have duplicate names, the size won't increase (because the data won't be unique) which means that we would have already seen the current name and it will return true.
ECMA Script 5 Version
If you don't have Set support, then you can use a normal JavaScript object itself, like this
var seen = {};
var hasDuplicates = values.some(function(currentObject) {
if (seen.hasOwnProperty(currentObject.name)) {
// Current name is already seen
return true;
}
// Current name is being seen for the first time
return (seen[currentObject.name] = false);
});
The same can be written succinctly, like this
var seen = {};
var hasDuplicates = values.some(function (currentObject) {
return seen.hasOwnProperty(currentObject.name)
|| (seen[currentObject.name] = false);
});
Note: In both the cases, we use Array.prototype.some because it will short-circuit. The moment it gets a truthy value from the function, it will return true immediately, it will not process rest of the elements.

In TS and ES6 you can create a new Set with the property to be unique and compare it's size to the original array.
const values = [
{ name: 'someName1' },
{ name: 'someName2' },
{ name: 'someName3' },
{ name: 'someName1' }
]
const uniqueValues = new Set(values.map(v => v.name));
if (uniqueValues.size < values.length) {
console.log('duplicates found')
}

To know if simple array has duplicates we can compare first and last indexes of the same value:
The function:
var hasDupsSimple = function(array) {
return array.some(function(value) { // .some will break as soon as duplicate found (no need to itterate over all array)
return array.indexOf(value) !== array.lastIndexOf(value); // comparing first and last indexes of the same value
})
}
Tests:
hasDupsSimple([1,2,3,4,2,7])
// => true
hasDupsSimple([1,2,3,4,8,7])
// => false
hasDupsSimple([1,"hello",3,"bye","hello",7])
// => true
For an array of objects we need to convert the objects values to a simple array first:
Converting array of objects to the simple array with map:
var hasDupsObjects = function(array) {
return array.map(function(value) {
return value.suit + value.rank
}).some(function(value, index, array) {
return array.indexOf(value) !== array.lastIndexOf(value);
})
}
Tests:
var cardHand = [
{ "suit":"spades", "rank":"ten" },
{ "suit":"diamonds", "rank":"ace" },
{ "suit":"hearts", "rank":"ten" },
{ "suit":"clubs", "rank":"two" },
{ "suit":"spades", "rank":"three" },
]
hasDupsObjects(cardHand);
// => false
var cardHand2 = [
{ "suit":"spades", "rank":"ten" },
{ "suit":"diamonds", "rank":"ace" },
{ "suit":"hearts", "rank":"ten" },
{ "suit":"clubs", "rank":"two" },
{ "suit":"spades", "rank":"ten" },
]
hasDupsObjects(cardHand2);
// => true

if you are looking for a boolean, the quickest way would be
var values = [
{ name: 'someName1' },
{ name: 'someName2' },
{ name: 'someName1' },
{ name: 'someName1' }
]
// solution
var hasDuplicate = false;
values.map(v => v.name).sort().sort((a, b) => {
if (a === b) hasDuplicate = true
})
console.log('hasDuplicate', hasDuplicate)

const values = [
{ name: 'someName1' },
{ name: 'someName2' },
{ name: 'someName4' },
{ name: 'someName4' }
];
const foundDuplicateName = values.find((nnn, index) =>{
return values.find((x, ind)=> x.name === nnn.name && index !== ind )
})
console.log(foundDuplicateName)
Found the first one duplicate name
const values = [
{ name: 'someName1' },
{ name: 'someName2' },
{ name: 'someName4' },
{ name: 'someName4' }
];
const foundDuplicateName = values.find((nnn, index) =>{
return values.find((x, ind)=> x.name === nnn.name && index !== ind )
})

You just need one line of code.
var values = [
{ name: 'someName1' },
{ name: 'someName2' },
{ name: 'someName4' },
{ name: 'someName2' }
];
let hasDuplicates = values.map(v => v.name).length > new Set(values.map(v => v.name)).size ? true : false;

Try an simple loop:
var repeat = [], tmp, i = 0;
while(i < values.length){
repeat.indexOf(tmp = values[i++].name) > -1 ? values.pop(i--) : repeat.push(tmp)
}
Demo

With Underscore.js A few ways with Underscore can be done. Here is one of them. Checking if the array is already unique.
function isNameUnique(values){
return _.uniq(values, function(v){ return v.name }).length == values.length
}
With vanilla JavaScript
By checking if there is no recurring names in the array.
function isNameUnique(values){
var names = values.map(function(v){ return v.name });
return !names.some(function(v){
return names.filter(function(w){ return w==v }).length>1
});
}

//checking duplicate elements in an array
var arr=[1,3,4,6,8,9,1,3,4,7];
var hp=new Map();
console.log(arr.sort());
var freq=0;
for(var i=1;i<arr.length;i++){
// console.log(arr[i-1]+" "+arr[i]);
if(arr[i]==arr[i-1]){
freq++;
}
else{
hp.set(arr[i-1],freq+1);
freq=0;
}
}
console.log(hp);

You can use map to return just the name, and then use this forEach trick to check if it exists at least twice:
var areAnyDuplicates = false;
values.map(function(obj) {
return obj.name;
}).forEach(function (element, index, arr) {
if (arr.indexOf(element) !== index) {
areAnyDuplicates = true;
}
});
Fiddle

Adding updated es6 function to check for unique and duplicate values in array. This function is modular and can be reused throughout the code base. Thanks to all the post above.
/* checks for unique keynames in array */
const checkForUnique = (arrToCheck, keyName) => {
/* make set to remove duplicates and compare to */
const uniqueValues = [...new Set(arrToCheck.map(v => v[keyName]))];
if(arrToCheck.length !== uniqueValues.length){
console.log('NOT UNIQUE')
return false
}
return true
}
let arr = [{name:'joshua'},{name:'tony'},{name:'joshua'}]
/* call function with arr and key to check for */
let isUnique = checkForUnique(arr,'name')

checkDuplicate(arr, item) {
const uniqueValues = new Set(arr.map((v) => v[item]));
return uniqueValues.size < arr.length;
},
console.log(this.checkDuplicate(this.dutyExemptionBase, 'CI_ExemptionType')); // true || false

It is quite interesting to work with arrays
You can use new Set() method to find duplicate values!
let's assume you have an array of objects like this...
let myArray = [
{ id: 0, name: "Jhon" },
{ id: 1, name: "sara" },
{ id: 2, name: "pop" },
{ id: 3, name: "sara" }
]
const findUnique = new Set(myArray.map(x => {
return x.name
}))
if(findUnique.size < myArray.length){
console.log("duplicates found!")
}else{
console.log("Done!")
}

const duplicateValues = [{ name: "abc" }, { name: "bcv" }, { name: "abc" }];
const isContainDuplicate = (params) => {
const removedDuplicate = new Set(params.map((el) => el.name));
return params.length !== removedDuplicate.size;
};
const isDuplicate = isContainDuplicate(duplicateValues);
console.log("isDuplicate");

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