JavaScript Array and it’s methods

The Array object is used to store multiple values in a single variable.

const cars = ["Hyundai", "Honda", "BMW", "Audi"];

Some Important Array Methods

1. concat():- Joins arrays and returns an array with the joined arrays

    const arr1 = ["Cecilie", "Lone"];
    const arr2 = ["Emil", "Tobias", "Linus"];
    const children = arr1.concat(arr2);
    console.log(children);
   
    //output: Cecilie,Lone,Emil,Tobias,Linus
   

2. constructor:- Returns the function that created the Array object's prototype

    const fruits = ["Banana", "Orange", "Apple", "Mango"];
    let text = fruits.constructor;
    console.log(text);
   
    //output: function Array() { [native code] }
   

3. filter():- Creates a new array with every element in an array that pass a test

    const ages = [32, 33, 16, 40];
   
    let result = ages.filter(checkAdult);
   
    function checkAdult(age) {
      return age >= 18;
    }
    console.log(result);
   
    //output: 32,33,40
   

4. find():- Returns the value of the first element in an array that pass a test

    const ages = [3, 10, 18, 20];
   
    let result = ages.find(checkAge);
   
    function checkAge(age) {
      return age > 18;
    }
    console.log(result);
   
    //output: 20
   

5. forEach():- Calls a function for each array element

    let text = "";
    const fruits = ["apple", "orange", "cherry"];
    fruits.forEach(myFunction);
   
    function myFunction(item, index) {
      text += index + ": " + item + "<br>"; 
    }
    console.log(text);
   
    //output: 0: apple
              1: orange
              2: cherry
   

6. findIndex():- Returns the index of the first element in an array that pass a test

    const ages = [3, 10, 18, 20];
   
    const result = ages.findIndex(checkAge);
   
    function checkAge(age) {
      return age > 18;
    }
    console.log(result);
   
    //output: 3
   

7. indexOf():- Search the array for an element and returns its position.

    const fruits = ["Banana", "Orange", "Apple", "Mango"];
    let index = fruits.indexOf("Apple");
   
    console.log(index);
    //output: 2
   

8. length:- Sets or returns the number of elements in an array

    const fruits = ["Banana", "Orange", "Apple", "Mango"];
    let length =  fruits.length;
    console.log(length);
   
    //output: 4
   

9. map():- Creates a new array with the result of calling a function for each array element

    const numbers = [4, 9, 16, 25];
    console.log(numbers.map(Math.sqrt));
   
    //output: 2,3,4,5
   

10. pop():- Removes the last element of an array, and returns that element

    const fruits = ["Banana", "Orange", "Apple", "Mango"];
    fruits.pop();
    console.log(fruits);
    
    output: Banana,Orange,Apple
    

11. push():- Adds new elements to the end of an array, and returns the new length

    const fruits = ["Banana", "Orange", "Apple", "Mango"];
    fruits.push("Kiwi");
    console.log(fruits);
    
    //output: Banana,Orange,Apple,Mango,Kiwi
    

12. slice():- Selects a part of an array, and returns the new array

    const fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"];
    const citrus = fruits.slice(1, 3);
    console.log(citrus);
    
    //output: Orange,Lemon
    

13. splice():- Adds/Removes elements from an array

    const fruits = ["Banana", "Orange", "Apple", "Mango"];
    
    // At position 2, add 2 elements: 
    fruits.splice(2, 0, "Lemon", "Kiwi");
    console.log(fruits);
    
    //output: Banana,Orange,Lemon,Kiwi,Apple,Mango
    

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