javascript reduce

final_example.js

const components = [
  {
    name: 'Button',
    styles: {
      color: 'white',
      backgroundColor: 'black',
      borderRadius: '20px'
    }
  },
  {
    name: 'TextInput',
    styles: {
      color: 'black',
      border: '2px solid'
    }
  },
  {
    name: 'Checkbox',
    styles: {
      color: 'deeppink'
    }
  }
];

const getComponentsMetadata = () => (
  components.reduce((acc, current) => ({
    ...acc,
    [current.name]: {
      ...current.styles
    }
  }), {})
);

final_output.js

{
  Button: {
    color: "white",
    borderRadius: "20px",
    backgroundColor: "black"
  },
  TextInput: { … },
  CheckBox: { … }
}

initialValue.js

const arr = [1, 2, 3, 4, 5, 6];
const sum = arr.reduce((acc, current) => acc + current, 10);

console.log(sum); // 31

join_names.js

const reducer = (accumulator, current, currentIndex, array) => {
  const prefix = currentIndex === array.length - 1 ? 'e ' : ', ';
  return `${accumulator}${prefix}${current}`;
}

function getJoinedNames(names) {
  return names.reduce(reducer);
}

console.log(getJoinedNames(['zezinho', 'luizinho', 'iguinho')]); // 'zezinho, luizinho e iguinho'

one_element.js

const arr = [1];
cont result = arr.reduce((acc, current) => 2 * (acc + current));

running.js

// 1 (valor inicial), 2 (valor atual) -> 1 + 2 
// 3 (valor anterior), 3 (valor atual) -> 3 + 3
// 6 (valor anterior), 4 (valor atual) -> 6 + 4
// 10 (valor anterior), 5 (valor atual) -> 10 + 5
// 15 (valor anterior), 6 (valor atual) -> 15 + 6

console.log(sum); // 21

simple.js

const arr = [1, 2, 3, 4, 5, 6];
const sum = arr.reduce((acc, current) => acc + current);

using_foreach.js

const arr = [1, 2, 3, 4, 5, 6];

let sum = 10;
arr.forEach(value => {
  sum += value;
})

console.log(sum); // -> 31