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How to add numbers inside an array. Total of Array Elements [duplicate]

This question already has answers here:
How to find the sum of an array of numbers
(59 answers)
Closed 1 year ago.
If I have an Array of some numbers.
Ex. var num =[123, 234, 12, 0, 23, 19];
How can I get a total of all these elements = 411;

Try This, it is the most recommended method to use.
Even in SAP -Fiori standard code, this method is used.
var num =[123, 234, 12, 0, 23, 19];
var total = num.reduce((a, b) => a + b, 0);

Javasript array functions with no arguments [duplicate]

This question already has answers here:
Create an array with random values
(24 answers)
Closed 3 years ago.
This is more like a silly question but I have to ask it.
It is a good practice to call an array function like map without arguments?
Let's say I already have an array 'x' on my code with a specified length and I want to make another array with the same length but with different content.
For example:
function generateRandomContent() { ... }
const x = [1, 2, 3, 4, 5]
const y = x.map(() => generateRandomContent())
// or
const z = Array(x.length).fill().map(() => { ... })
Of course I could pass an argument and never use it, but it is there a good way and a bad way to do it?

You should not use .map here. A mapping operation is when you take some input and generate a new output. So you have a relation that looks like this x -> y for a single element, then you apply it to the entire array to generate a new array using the same mapping rule:
const input = [104, 101, 108, 108, 111, 32, 119, 111, 114, 108, 100];
//mapping relationship
const toCharacter = x => String.fromCharCode(x);
const result = input.map(toCharacter);
console.log(result.join(''))
If you just want to create a new array based on the length of the original but with totally unrelated content, then you are better off to use Array.from which can create an array with a given size and takes a second argument that will fill it with content:
function generateRandomContent() {
return Math.floor(Math.random() * 100);
}
const x = [1, 2, 3, 4, 5]
const y = Array.from({length: x.length}, () => generateRandomContent());
//or just pass the function reference
const z = Array.from({length: x.length}, generateRandomContent);
console.log(y);
console.log(z);

Can I create a custom function and call it on an array i JavaScript [duplicate]

This question already has answers here:
adding custom functions into Array.prototype
(7 answers)
Closed 3 years ago.
How can I create a functions within JavaScript, that i can then use and chain with others to get results from an array.
I have tried creating a class with multiple methods that can be chain together but that wont allow me to call the functions directly on the array itself.
Example:
[23,45,87,89,21,234,1,2,6,7].CustomFuncEvenNumbers().CustomFuncOrderNumbers()

You can create the custom function using prototype but to chain another function you need to explicitly return from your custom function , else it will return undefined
let arr = [23, 45, 87, 89, 21, 234, 1, 2, 6, 7];
Array.prototype.CustomFuncEvenNumbers = function() {
return this.filter(function(item) {
return item % 2 === 0
})
}
let k = arr.CustomFuncEvenNumbers().map(item => item * 2);
console.log(k)

Iterate over an array and get the transformed array as a result [duplicate]

This question already has answers here:
From an array of objects, extract value of a property as array
(24 answers)
Return array value with forEach() [duplicate]
(1 answer)
Closed 5 years ago.
So there are a lot of questions about iterating over an array, but I found none that says how to get the transformed array back as the left side variable. I can always do a standard for loop with indicies but I was wondering if I could use something like a .foreach that would return a transformed array.
Psedo example: I have an array points which are made up of an object Phaser.Point
Such that I can write the following code
x = new Phaser.Polygon(points.foreach(function (point) {
return new Phaser.Point(point.x+5, point.y+5)
});
new Phaser.Polygon takes an array of Phaser.Point objects

In this case, you may want to use Array.prototype.map(). Here is an example from MDN:
var numbers = [1, 5, 10, 15];
var roots = numbers.map(function(x) {
return x * 2;
});
// roots is now [2, 10, 20, 30]
// numbers is still [1, 5, 10, 15]
In your case:
x = new Phaser.Polygon(points.map(function (point) {
return new Phaser.Point(point.x+5, point.y+5)
});
References:
Array.prototype.map()

You can use Array.map. Array.map returns new array.

Javascript - Check if 2 items exist in array [duplicate]

This question already has answers here:
Javascript - check array for value [duplicate]
(3 answers)
How do I check if an array includes a value in JavaScript?
(60 answers)
Closed 6 years ago.
In Javascript, how can I ensure that the array of ages has both ages 10 and 18 and not just one.
var ages = [3, 10, 18, 20];
ages.filter(age => age === 10 || age === 18); // returns 10 and 18
ages.filter(age => age === 10 && age === 18); // returns null
The && doesn't ensure that both exist, as it returns null. I know I can use 2 different ages.find/filter and check the combined result, but I am wondering if there is a more elegant way of doing this in a single statement.
To clarify, in the ages array, if I check for 10 (exists) and 21 (doesn't exist), it should return null or false, as one of them does not exist.

You have to use includes function:
var ages = [3, 10, 18, 20];
console.log(ages.includes(10) && ages.includes(18));
Another method is to use indexOf method:
arr.indexOf(searchElement)
arr.indexOf(searchElement, fromIndex)
var ages = [3, 10, 18, 20];
console.log(ages.indexOf(10)!=-1 && ages.indexOf(18)!=-1);
findIndex is another method that you can use.It actions like indexOf, but there are some differences:
Array.prototype.indexOf() expects a value as parameter. This is usefull for arrays of primitive types,such as Number, String, Boolean.
Array.prototype.findIndex() have a callback function as first parameter. This is usefull specially when you have array of objects.
var ages = [3, 10, 18, 20];
var bool=ages.findIndex(a=>a==10)!=-1 && ages.findIndex(a=>a==18)!=-1;
console.log(bool);