Reduce javascript

Javascript reduce

var array = [36, 25, 6, 15];

array.reduce(function(accumulator, currentValue) {
  return accumulator + currentValue;
}, 0); // 36 + 25 + 6 + 15 = 82

153

Source: grepper.com

Reduce()

const array1 = [1, 2, 3, 4];
const reducer = (accumulator, currentValue) => accumulator + currentValue;

// 1 + 2 + 3 + 4
console.log(array1.reduce(reducer));
// expected output: 10

// 5 + 1 + 2 + 3 + 4
console.log(array1.reduce(reducer, 5));
// expected output: 15

Source: developer.mozilla.org

Javascript reduce

[3, 2.1, 5, 8].reduce((total, number) => total + number, 0)

// loop 1: 0 + 3
// loop 2: 3 + 2.1
// loop 3: 5.1 + 5
// loop 4: 10.1 + 8
// returns 18.1

Source: dev.to

Javascript reduce

const sum = array.reduce((accumulator, element) => {
  return accumulator + element;
}, 0);

Source: grepper.com

JavaScript Array Methods .reduce()

const list = [1, 2, 3, 4, 5];
console.log(list.reduce((number, nextNumber) => number + nextNumber));
// --> 15

Source: github.com

Syntax of reduce in js

[1,2,3,4,5].reduce((acc, current)=>acc+current, 0)

Source: grepper.com

Array reduce

arr.reduce(callback( accumulator, currentValue[, index[, array]] ) {
  // return result from executing something for accumulator or currentValue
}[, initialValue]);

Source: grepper.com

Reduce method

The reduce() method executes a reducer function (that you provide) on each element of the array, resulting in single output value.

The reducer function takes four arguments:
Accumulator (acc)
Current Value (cur)
Current Index (idx)
Source Array (src)

//syntax
arr.reduce(callback( accumulator, currentValue, [, index[, array]] )[, initialValue])
//example flatten an array

let flattened = [[0, 1], [2, 3], [4, 5]].reduce(
  ( accumulator, currentValue ) => accumulator.concat(currentValue),
  []
)

Source: developer.mozilla.org

JavaScript Reduce

const arr = [1, 2, 3]
const result = arr.reduce((acc, curr) => acc + curr, 0)
// 1 + 2 + 3 = 6
console.log(result)

Source: grepper.com

.reduce javascript

reduce function sample solution

Source: grepper.com

THE REDUCE() METHOD IN JAVASCRIPT

/*
This method takes a callback that takes two parameters,
one that represents the element from the last iteration and the other is the current
element of the iteration
*/

let nums = [2,4,6,8,3,5]

let result = nums.reduce((prev,curr)=>prev+curr)
console.log(result); // 28

Source: blog.devgenius.io

Js .reducer method

const arrayOfNumbers = [1, 2, 3, 4];
 
const sum = arrayOfNumbers.reduce((accumulator, currentValue) => {  
  return accumulator + currentValue;
});
 
console.log(sum); // 10

Source: codecademy.com

Reduce in javascript

// Reduce in javascript advance
// output: { '22': 2, '24': 2, '26': 1 }
const user = [
  {name:"Abhishek",age:24},
  {name:"Dhruval",age:22},
  {name:"Anish",age:26},
  {name:"Aakash",age:22},
  {name:"Darshil",age:24},
]
const newUser = user.reduce((acc,cur)=>{
  if(acc[cur.age]){
    acc[cur.age] = acc[cur.age] +1 
  }
  else{
    acc[cur.age] = 1 
  }
  return acc;
},{})

console.log(newUser)

Source: grepper.com

Js array reduce

// Arrow function
reduce((previousValue, currentValue) => { /* ... */ } )
reduce((previousValue, currentValue, currentIndex) => { /* ... */ } )
reduce((previousValue, currentValue, currentIndex, array) => { /* ... */ } )
reduce((previousValue, currentValue, currentIndex, array) => { /* ... */ }, initialValue)

// Callback function
reduce(callbackFn)
reduce(callbackFn, initialValue)

// Inline callback function
reduce(function(previousValue, currentValue) { /* ... */ })
reduce(function(previousValue, currentValue, currentIndex) { /* ... */ })
reduce(function(previousValue, currentValue, currentIndex, array) { /* ... */ })
reduce(function(previousValue, currentValue, currentIndex, array) { /* ... */ }, initialValue)

Source: developer.mozilla.org

Reduce method

function reduce(array, combine, start) {
  let current = start;
  for (let element of array) {
    current = combine(current, element);
  }
  return current;
}

console.log(reduce([1, 2, 3, 4], (a, b) => a + b, 0));
// → 10

Source: eloquentjavascript.net

Javascript reduce

let arr = [1,2,3]

/*
reduce takes in a callback function, which takes in an accumulator
and a currentValue.

accumulator = return value of the previous iteration
currentValue = current value in the array

*/

// So for example, this would return the total sum:

const totalSum = arr.reduce(function(accumulator, currentVal) {
	return accumulator + currentVal
}, 0);

> totalSum == 0 + 1 + 2 + 3 == 6

/* 
The '0' after the callback is the starting value of whatever is being 
accumulated, if omitted it will default to whatever the first value in 
the array is, i.e: 

> totalSum == 1 + 2 + 3 == 6

if the starting value was set to -1 for ex, the totalSum would be:
> totalSum == -1 + 1 + 2 + 3 == 5
*/


// arr.reduceRight does the same thing, just from right to left

Source: grepper.com

Using Array.reduce() method

// define a reusable function
const calculateSum = (arr) => {
    return arr.reduce((total, current) => {
        return total + current;
    }, 0);
}

// try it
console.log(calculateSum([1, 2, 3, 4, 5]));

Source: kindacode.com

JS Reduce example

const grades = [60, 55, 80, 90, 99, 92, 75, 72];
const total = grades.reduce(sum);
function sum(acc, grade) {  
return acc + grade;
}
const count = grades.length;
const letterGradeCount = grades.reduce(groupByGrade, {});
function groupByGrade(acc, grade) {  
const { a = 0, b = 0, c = 0, d = 0, f = 0 } = acc;  
if (grade >= 90) {    
return { ...acc, a: a + 1 };  
} else if (grade >= 80) {    
return { ...acc, b: b + 1 };  
} else if (grade >= 70) {    return { ...acc, c: c + 1 };  
} else if (grade >= 60) {    return { ...acc, d: d + 1 };  
} else {    return { ...acc, f: f + 1 };  }}
console.log(total, total / count, letterGradeCount);

Source: jsbin.com

Javascript reduce

You can return whatever you want from reduce method, reduce array method good for computational problems
const arr = [36, 25, 6, 15];
array.reduce(function(accumulator, currentValue) {
  return accumulator + currentValue;
}, 0); // this will return Number
array.reduce(function(accumulator, currentValue) {
  return accumulator + currentValue;
}, []); // this will return array
let {total} = array.reduce(function(accumulator, currentValue) {
  let {currentVal} = currentValue
  return accumulator + currentVal;
}, {
total: 0
}); // this will return object
And one additional rule is always always retrun the first param, which do arithmetic operations.

Source: grepper.com

Javascript reduce function array

let numbers = [1, 2, 3];
let sum = numbers.reduce(function (previousValue, currentValue) {
    return previousValue + currentValue;
});

Source: javascripttutorial.net

Reduce method

[0, 1, 2, 3, 4].reduce(
  (accumulateur, valeurCourante) => accumulateur + valeurCourante;
);

Source: developer.mozilla.org

Array reduce javascript

const numbers = [260, 25, 35];

console.log(numbers.reduce(myFunc))

function myFunc(total, num) {
  return total - num;
}
/*console.log will show 200 since the first element minus 35 and minus 25 is 260-25-35=200*/
/*while the name is "reduce", you do NOT have to subtract. Reduce() is more about "take the first element as total, and do something(whatever the function says) to it for each of the remaining elements; the remaining elements will be identified as the second parameter num for the function myFunc, you do whatever once for all remaining elements*/

Source: grepper.com

Reduce method

const doubledAndSummed = [1, 2, 3].reduce(function(accumulator, element){ return element * 2 + accumulator}, 0)
// => 12

Source: my.learn.co

Reduce function javascript

array.reduce(function(acumulador, elementoAtual, indexAtual, arrayOriginal), valorInicial)

Source: medium.com

JavaScript Array reduce()

const numbers = [45, 4, 9, 16, 25];
let sum = numbers.reduce(myFunction);

function myFunction(total, value, index, array) {
  return total + value;
}

-1

Source: grepper.com

Reduce function in javascript

reduce method does not changed original array

-1

Source: grepper.com

Reduce function in javascript

reduce function

-2

Source: grepper.com

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