Hoow to remove Items from the Array dynamically? - javascript

I need a function which removes some items from array dynamically.
for example:
const array = [1, 2, 3, 4, 6, 1, 3, 9, 5, 7, 6, 8, etc.];
I need to remove all items before item "6", but after remove it stop the function and don't remove next items before next item "6".
There are word's array in project and I need to filter it. need to remove all items before one specific word.

findIndex and slice will do it
const array = [1, 2, 3, 4, 6, 1, 3, 9, 5, 7, 6, 8];
const findNum = 6;
const idx = array.findIndex(num => num === findNum)
console.log(array.slice(idx))

Related

Compare how much items are equals in arrays using Javascript

what's up? I hope you going well.
So, my question is, I have a array with number that I have to compare with another arrays (like 1 to X), what is the best way to:
1º compare the arrays and retrieve the numbers that are equals.
2º the numbers of elements that are equal (without using .length on the array with numbers are equals).
Example:
Array 1 = [1, 3, 4, 5, 6, 7, 8, 9, 11, 13, 16]
Array 2 = [1, 2, 3, 7, 9, 12, 16, 17]
That way, the total numbers is 5
And the numbers are: [1, 3, 7, 9, 16]
My method is using forEach and compare each item and using .length on the array with the numbers that are equals, there's another way or best way to do this?
Another example using more arrays:
Arr1 = [1, 2, 3, 5, 6, 7, 8, 10, 15]
Arr2 = [
[1, 3, 5, 7, 8, 9, 10, 11, 12],
[2, 5, 6, 7, 9, 10],
[1, 3, 5, 7, 10, 11, 13, 14, 15]
]
// Output
6, [1, 3, 5, 7, 8, 10]
5, [2, 5, 6, 7, 10]
7, [1, 3, 5, 6, 7, 10, 15]
Thanks for the answer.
I like using Set for this purpose. You can create a Set from your first array and then any lookup in that Set (using Set.has) is O(1) efficiency.
const arr1 = [1, 3, 4, 5, 6, 7, 8, 9, 11, 13, 16];
const arr2 = [1, 2, 3, 7, 9, 12, 16, 17];
const arr1Items = new Set(arr1);
const matched = arr2.filter(el => arr1Items.has(el));
console.log(matched.length, matched);
Arr2 is an array, not an object, your code would change accordingly
Arr1 = [1, 2, 3, 5, 6, 7, 8, 10, 15]
Arr2 = [
[1, 3, 5, 7, 8, 9, 10, 11, 12,],
[2, 5, 6, 7, 9, 10],
[1, 3, 5, 7, 10, 11, 13, 14, 15,]
]
Given that, the solution is a oneliner:
res = Arr2.map(a=>a.filter(x=>Arr1.indexOf(x)!=-1).length)
It should be straightforward but, just in case:
The [].indexOf(el) method give you the position of the parameter in the array, if that element is not present it will return -1. Therefore, the function
x => Arr1.indexOf(x)!=-1
returns true or false if x is present or not in the Arr1 array
The [].filter(fn) method use the fn function to evaluate every array element and give as result an array with the evaluated true elements.
a.filter(x => Arr1.indexOf(x)!=-1)
Means give me all the elements of array a presents in Arr1
Now we just have to count the lenght of that array
a.filter(x => Arr1.indexOf(x)!=-1).length
and pass this count to the [].map(fn) method to have the result we need.
The function I wrote below will give the results you want, but remember the function returns an array of arrays, even if the second parameter had only one array or was an array of elements instead of array of arrays (Works for both).
Arr1 = [1, 2, 3, 5, 6, 7, 8, 10, 15]
Arr2 = [
[1, 3, 5, 7, 8, 9, 10, 11, 12],
[2, 5, 6, 7, 9, 10],
[1, 3, 5, 7, 10, 11, 13, 14, 15]
]
Arr3 = [1, 5, 6, 9, 12, 15, 17]
function check(base_array,search_values)
{
if(base_array.length===0 || search_values.length===0)
{
return [];
}
else if(Array.isArray(search_values[0]))// Check if second parameter is an array of arrays.
{
var result=[];
search_values.forEach(search=>{
var result_sub=[];
search.forEach(key=>{
if(base_array.includes(key))
{
result_sub.push(key);
}
});
result.push(result_sub);
});
return result;
}
else
{
var result=[];
search_values.forEach(key=>{
if(base_array.includes(key))
{
result.push(key);
}
});
return [result];
}
}
console.log("Array of Arrays");
console.log(check(Arr1,Arr2));
console.log("Array of Elements");
console.log(check(Arr1,Arr3));
From the returned result you can loop through the value to get the elements and the number of elements by checking length of array.
result.forEach(element=>{
console.log(result.length, result);// number of elements doesn't have to be passed
});
What the Function does is it checks if any array is empty , then returns empty array [], if the second array is an array of arrays it loops through each array and then to each element in the sub array and checks if it exists in the first array, else if the array was array of elements, then it just loops through the elements and checks if it exists in the first array. And returns the result stored

How to remove array based on specific value?

I have two arrays.
var allAuth = [1, 2, 3, 4, 5, 6, 7, 8]
let thomasauth = [2, 3, 4, 5, 6, 7, 8]
let res = allAuth.filter(f => !thomasauth.includes(f));
I am returning the missing matching value from allAuth array which is 1.
I want to remove 1 from allAuth array.
I currently have
let filteredArr = allAuth.filter(e => e !== res)
but this just gives me back the allAuth array without anything being removed.
my desired output should be
let filteredArr = [2,3,4,5,6,7,8]
Can anyone help? Thanks.
Change !thomasauth.includes(f) to thomasauth.includes(f) so to filter only the included items (1 will be excepted in that case.)
var allAuth = [1, 2, 3, 4, 5, 6, 7, 8]
let thomasauth = [2, 3, 4, 5, 6, 7, 8]
let res = allAuth.filter(f => thomasauth.includes(f));
console.log(res);
Have you tried out your code? You will see that res is actually an array containing the values you want to remove ([1]) and not a single scalar value.
So I think you intended to do this:
let filteredArr = allAuth.filter(e => !res.includes(e));
var allAuth = [1, 2, 3, 4, 5, 6, 7, 8];
let thomasauth = [2, 3, 4, 5, 6, 7, 8];
let result = allAuth.filter(val => thomasauth.indexOf(val) !== -1);
console.log(result);

Relative Sort Array Javascript

I am working on a problem on LeetCode and having some troubles
https://leetcode.com/problems/relative-sort-array/
Instructions:
Given two arrays arr1 and arr2, the elements of arr2 are distinct, and all elements in arr2 are also in arr1.
Sort the elements of arr1 such that the relative ordering of items in arr1 are the same as in arr2. Elements that don't appear in arr2 should be placed at the end of arr1 in ascending order.
Example 1:
Input: arr1 = [2,3,1,3,2,4,6,7,9,2,19], arr2 = [2,1,4,3,9,6]
Output: [2,2,2,1,4,3,3,9,6,7,19]
my attempt:
var relativeSortArray = function(arr1, arr2) {
let arr =[]
let end =[]
for (i=0; i<arr2.length; i++){
for (j=0; j<arr1.length; j++){
if(arr2[i] == arr1[j]){
arr.push(arr1[j])
}else{
end.push(arr1[j])
}
}
}
end.sort((a,b) => a-b)
console.log(end)
return arr
};
The If conditional works but the else condition isn't and I can't figure out why.
I think console.log(end) should give me the two numbers not in arr2 but it instead gives me:
[
1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3,
3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 6,
6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 9, 9,
9, 9, 9, 19, 19, 19, 19, 19, 19
]
Why is this happening?
Thanks!!!
You could take an object for the position of a value and take a large value like Number.MAX_VALUE as default value. If the delta is zero sort by value.
Taking a delta is a standard by using Array#sort. This returns a value smaller than zero, zero or greater than zero, depending on the values. The sort method receives this values and keeps or swaps the values.
const
relativeSort = (array, given) => {
const order = Object.fromEntries(given.map((v, i) => [v, i + 1]));
return array.sort((a, b) =>
(order[a] || Number.MAX_VALUE) - (order[b] || Number.MAX_VALUE) ||
a - b
);
};
console.log(...relativeSort([2, 3, 1, 3, 2, 4, 6, 7, 9, 2, 19], [2, 1, 4, 3, 9, 6]));
In each iteration of arr2:
all the numbers that are different from the current number are pushed to the end array
For example,
First iteration - compare number (2) and you will end up with:
arr: [2,2,2]
end: [3,1,3,4,6,7,9,19]
Second iteration - compare number (1) and you will end up with:
arr: [2,2,2,1]
end: [3,1,3,4,6,7,9,19] + [2,3,3,2,4,6,7,9,2,19]
try to debug your code to follow the flow
class Solution:
def relativeSortArray(self, arr1: list[int], arr2: list[int]) -> list[int]:
arr = []
for i in arr2:
value = arr1.count(i)
for j in range(value):
arr.append(i)
arr1.remove(i)
arr1.sort()
return arr+arr1
obj = Solution()
arr1 = [28,6,22,8,44,17]
arr2 = [22,28,8,6]
result = obj.relativeSortArray(arr1,arr2)
print(result)

Push duplicate values to another array in JavaScript

I have an array, which contains duplicate values. How can I push duplicates in to another array?
let arr1 = [1, 5, 3, 6, 9, 5, 1, 4, 2, 7, 9], and duplicates array should be dupArr = [1, 5, 9]
You could filter the array by storing the previous checked values in a Set, which is here a closure.
var array = [1, 5, 3, 6, 9, 5, 1, 4, 2, 7, 9],
duplicates = array.filter((s => v => s.has(v) || !s.add(v))(new Set));
console.log(duplicates);

trasformation index array in value

example value return:
array[1]=1
array[5]=5
array[12]=[1, 2]
array[85]=[8, 5]
array[7453]=[7, 4, 5, 3]
array[8987556322415]=[8, 9, 8, 7, 5, 5, 6, 3, 2, 2, 4, 1, 5]
Which is the best way to convert the index to an array with single decimal value (only one number for every index)
var array=[30];
function getVal(array){
for ( i=0; i<i.length; i++ ){
....
} return array;
}
getVal(array);
-> array [1] = 0
-> array [0] = 3
Cast it to string, and since string is an array of char, you can manullay parse them back to numbers.
var index = 8987556322415;
var arr = index.toString().split("").map(char=>parseInt(char));
console.log(arr)//[8, 9, 8, 7, 5, 5, 6, 3, 2, 2, 4, 1, 5]
Here is a JSBin for you

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