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JavaScript filter method not giving unique result [closed]

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Closed 9 months ago.
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i am trying to filter the unique ones from a given array using filter method but its throwing an empty array, here is the code
function dual(a) {
if (Array.isArray(a)) {
let unique = a.filter((val, index) => {
a.indexOf(val) == index
})
return unique;
}
}
console.log(dual([3, 1, 1, 2, 2])) //expected result [3,1,2] but showing []

You may use Set() to create a unique array:
const arr = [3,1,1,2,2]
var uniqueArray = [...new Set(arr)]
console.log(uniqueArray)

You are missing return statements from both your function and your filter array method.

Get value from an array using find in JavaScript [closed]

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Closed 11 months ago.
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I've got an array:
test = [{'id':'73','name':'bar', 'contact': [{'name':'barFoo','tel':'3333'}]},{'id':'45','name':'foo', 'contact':[]}]
I try to get contact.tel in first object with 'id':'73'
I'm using find method :
let contactTel = test.find(x => x.id === '73').contact.tel;
but it dosen't work. What I'm doing wrong ?

it should be like this
const test = [{'id':'73','name':'bar', 'contact': [{'name':'barFoo','tel':'3333'}]},{'id':'45','name':'foo', 'contact':[]}]
let contactTel = test.find(x => x.id === '73').contact[0].tel;
console.log(contactTel)

Javascript Array.filter() and Array.some() [closed]

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Closed 2 years ago.
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I want to filter an array of files by their extensions.
I have written following code:
const exts = ['.log, ts']
const files = [
'a.ts', 'b.xml', 'c.log'
]
const res = files.filter(f => {
return exts.some(e => {
return f.endsWith(e)
})
})
console.log(res)
In my opinion, it should output['a.ts', 'c.log'].
But I get an empty array.
I am looking at this since hours. I don't get it. Please help me.. What's wrong ?

You need more than one string in the array for exts
const exts = ['.log', '.ts']
const
exts = ['.log', '.ts'],
files = ['a.ts', 'b.xml', 'c.log'],
res = files.filter(f => exts.some(e => f.endsWith(e)));
console.log(res);

array replaces instead of concatenating values [closed]

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Closed 2 years ago.
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I have this array declared as
rowData = []
I want to update this array with a forloop but it keeps replacing the values instead of updating it. I guess I'm doing something wrong.
rowDataDefs(){
for (let to of this.detailedOrders){
console.debug(to)
this.rowData = [
{table_no: to.table.tableNo, order_no: to.orderNo, date_time: to.table.createdDate }
]
}
}

rowDataDefs(){
for (let to of this.detailedOrders){
console.debug(to)
this.rowData.push(
{table_no: to.table.tableNo, order_no: to.orderNo, date_time: to.table.createdDate });
}
}

You need to use array.push() instead of replacing the same index(0th index) value every time.
rowDataDefs(){
for (let to of this.detailedOrders){
console.debug(to)
this.rowData.push(
{
table_no: to.table.tableNo,
order_no: to.orderNo,
date_time: to.table.createdDate
}
)
}
return this.rowData;
}

Simple javascript for selecting random element out of array outputting "undefined" on 2 elements (jsfiddle included) [closed]

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Closed 6 years ago.
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Below is my code, for some reason it outputs undefined for ['6'] & ['7'], all the other ones work. I don't understand what is going wrong.
var array = [
['1'],
['2'],
['3'],
['4'],
['5'],
['6']
['7'],
['8'],
['9'],
['10']
];
if(document.getElementById("random-element")) {
var rand = array[Math.floor(Math.random() * array.length)];
document.getElementById('random-element').innerHTML = rand;
}
https://jsfiddle.net/ggky7a03/

You missed a comma in your array, which will explain why those 2 values are not returning (they don't exist)
Side note, array is a reserved word in JS, so you can't (shouldn't) use it for your variable name, so change it to
var myAwesomeArray = [
// or similar
Here's your fixed code