javascript foreach over array of objects code example

Example 1: foreach in javascript

///Simple One
var a = ["a", "b", "c"];
a.forEach(function(entry) {
    console.log(entry);
});


///Function  concept

var fruits = ["apple", "orange", "cherry"];
fruits.forEach(myFunction);

function myFunction(item, index) {
  document.getElementById("demo").innerHTML += index + ":" + item + "<br>";
}

Example 2: iterate over array of objects javascript

// Transform to a new array

const myArray = [{x:100}, {x:200}, {x:300}];

const newArray= myArray.map(element => element.x);
console.log(newArray); // [100, 200, 300]

Example 3: looping through an object of objects with arrays

let storeItems = {   
    eggs: {
      price: 3.77, quantity: 30
    },   
                  
    milk: {
      price: 2.22, quantity: 23
    },   
                   
    butter: {
      price: 2.00, quantity: 22
    },       
                   
    carrots: {
      price: 3.00, quantity: 11
    },   
                   
    beef: {
      price: 6.18, quantity: 34
    },   
    chicken: {
      price: 5.44, quantity: 34
    }
  };
  
  for(let item in storeItems) {   
    console.log(`${storeItems[item].quantity} ${item}s each cost ${storeItems[item].price}`);
}
  
  
// //OUTPUT:“30 eggs each cost 3.77”
// “23 milks each cost 2.22”
// “22 butters each cost 2”
// “11 carrots each cost 3”
// “34 beefs each cost 6.18”
// “34 chickens each cost 5.44”

Example 4: iterate over array of objects javascript

// Just loop through an array

const myArray = [{x:100}, {x:200}, {x:300}];

myArray.forEach((element, index, array) => {
    console.log(element.x); // 100, 200, 300
    console.log(index); // 0, 1, 2
    console.log(array); // same myArray object 3 times
});

Example 5: iterate over array of objects javascript

// Sum up a particular property, and calculate its average

const myArray = [{x:100}, {x:200}, {x:300}];

const sum = myArray.map(element => element.x).reduce((a, b) => a + b, 0);
console.log(sum); // 600 = 0 + 100 + 200 + 300

const average = sum / myArray.length;
console.log(average); // 200

Example 6: iterate over array of objects javascript

// Count the number of each category

const people = [
    {name: 'John', group: 'A'}, 
    {name: 'Andrew', group: 'C'}, 
    {name: 'Peter', group: 'A'}, 
    {name: 'James', group: 'B'}, 
    {name: 'Hanna', group: 'A'}, 
    {name: 'Adam', group: 'B'}];

const groupInfo = people.reduce((groups, person) => {
    const {A = 0, B = 0, C = 0} = groups;
    if (person.group === 'A') {
        return {...groups, A: A + 1};
    } else if (person.group === 'B') {
        return {...groups, B: B + 1};
    } else {
        return {...groups, C: C + 1};
    }
}, {});

console.log(groupInfo); // {A: 3, C: 1, B: 2}