Arrays

Declaring arrays

let a1 = [1, 2, 3, 4, 5, 6];
let a2 = [11, 22, 33, 44, 55, 66];

Adding and removing at last index

a1.push(7);
a1.pop();

Adding and removing at index 0

a1.unshift(0);
a1.shift();

Adding and removing any where in array using index number

a1[1] = 22;
a1.splice(1, 1); // postion, number of element
console.log(a1);
a1.forEach((item, index) =>
  console.log("Value at index " + index + " is " + item)
);
a1.forEach((item, index) => {
  if (item % 2 == 0) {
    console.log("Even number found at index" + index);
  } else {
    console.log("Odd number found at index" + index);
  }
});

Array concatenation

console.log(a1.concat(a2));

every

console.log(
  a1.every((item) => {
    if (item > 0) {
      return true;
    }
  })
);

fill

console.log(a1.fill(0, 2, 4));

filter

var a2_even = a2.filter((item) => {
  if (item % 2 == 0) {
    return item;
  }
});
var a2_odd = a2.filter((item) => {
  if (item % 2 != 0) {
    return item;
  }
});
console.log(a2_even);
console.log(a2_odd);

find - returns first value which staisfies the given testing function

console.log(
  a2.find((item) => {
    if (item > 20) {
      return item;
    }
  })
);

indexOf

console.log(a2.indexOf(22));

includes

console.log(a2.includes(22));

join

console.log(a2.join(","));

map

console.log(a2.map((item) => item ** 2));

reduce

• Reduce is a higher-order function that is used to transform an array of values into a single value.

const numbers = [1, 2, 3, 4, 5];
const sum = numbers.reduce((accumulator, currentValue) => {
  return accumulator + currentValue;
});
console.log(sum); // Output: 15