arrayFunction.js

//Array.map() function for traversing the array and perform certain tasks
let arrayMap1 = [1,2,3,4,5];
let arrayMap2 = arrayMap1.map((element)=>{
    return element*2;
});
//Will print [ 2, 4, 6, 8, 10 ]
console.log(arrayMap2);

//Array.filter() function returns the element only if the condition is true
let arrayFilter1 = [1,2,3,4,5];
let arrayFilter2 = arrayFilter1.filter((element) => {
    if(element > 2){
        return true;
    }
    return false;
});
//Will print only [3,4,5] coz 1 & 2 are lesser than 2;
console.log(arrayFilter2);

//Array.forEach() function does not need to return anything. It is used like loops only. The major difference between .map() fucntion and .forEach() function is in .map() function you need second array to store all your values whereas .forEach() just traverses it
let arrayForEach = ["kaiwalya",18,"koparkar","javascript"]
//Will print 
/*
kaiwalya
18
koparkar
javascript

**Notice there are no [] around the result**
*/
arrayForEach.forEach((element)=>{
    console.log(element);//only tranversing purpose
});

//Array.reduce() this is used when you need to compress all the array elements into one value. For eg: Adding all the elements in the array and return sum
let arrayReduce = [1,2,3,4,5,6,7,8,9,10];
let result = arrayReduce.reduce((addition,element)=>{
    return addition+element;
});//fist time value of addition = 1 (1st element of array) and element = 2 (2nd element of the array);
console.log(result);

let arrayReduce2 = [1,2,3,4,5,6,7,8,9,10];
let result2 = arrayReduce2.reduce((addition2,element2)=>{
    return addition2+element2;
},0);//fist time value of addition = 0 (the provided 0 after {}) and element = 1 (1st element of the array);
//This is because sometimes you need to provide the value of the addition
console.log(result2);

//Array.indexOf() this is used to find the index at which the passed element resides on (Returns integer)
let arrayIndexOf = ["hello","my","name","is","kaiwalya"];
//Indexes             0      1     2      3       4
console.log(arrayIndexOf.indexOf("kaiwalya"));//prints 4

//Array.includes() this is used to check if the element exists in the array or not. (Returns boolean)
let arrayIncludes = ["hello","my","name","is","kaiwalya"];
console.log(arrayIncludes.includes("kaiwalya"));//prints true

//Array.find() this is used to find the element especially when you have objects
let students = [
    {
        name:"kaiwalya",
        age:18
    },
    {
        name:"ABC",
        age:18
    },
    {
        name:"XYZ",
        age:18
    },
    {
        name:"PQR",
        age:19
    },
]

var stud = students.find(s => {
    return s.age==18; //prints kaiwalya 18 coz its the first occurance.
});

console.log(stud);