Array and loops :-
const languages = ['javaScript','Python','C++']
Lenght
console.log(languages.length);
adding arrays
languages.push('Dart')
languages.unshift('Java')
removing arrays
languages.pop()
languages.shift()
console.log(languages);
LOOPS :-
const actors = [
{
name : "Actor 1",
payment : 100
},
{
name : "Actor 2",
payment : 200
},
{
name : "Actor 3",
payment : 150
},
];
For Loop
for (let i = 0; i < actors.length; i++){
actors[i].payment = actors[i].payment - 10;
}
console.log(actors);
ForEach Loop
actors.forEach((actor)=> {
actor.name = "Name changed"
actor.payment = actor.payment - 50;
console.log(actor);
})
ForOff Loops :-
for (let actor of actors){
actor.payment = actor.payment - 10;
console.log(actor);
}
Filter
const student = [
{
name : "Student 1",
marks : 45
},
{
name : "Student 2",
marks : 67
},
{
name : "Student 3",
marks : 30
},
]
let failed = student.filter((student) => {
if(student.marks < 45){
return true;
}else
{
return false;
}
})
console.log(failed);
MAP
const users = [
{
fName : "John",
lName : "Doe"
},
{
fName : "Jane",
lName : "Doe"
}
];
const finalUsers = users.map((user)=>{
return {
fullname : `${user.fName} ${user.lName}`
};
});
console.log(finalUsers);
Reduce
let movies = [
{
name : "Interstellar",
budget : 100
},
{
name : "Social",
budget : 150
},
{
name : "Matrix",
budget : 300
},
]
using forEach for example
let total = 0;
movies.forEach((movie) =>{
total = total + movie.budget
})
using reduce
const total = movies.reduce((acc,movie)=>{
acc = acc+ movie.budget;
return acc;
},0)
console.log(total);
IndexOf
it return index or -1
const admins = [2,1,5];
const user = {
name : 'xyz',
id : 5,
}
const isAdmin = admins.indexOf(user.id) > -1;
console.log(isAdmin);
Includes
Better than IndexOf
const admins = [2,1,5];
const user = {
name : 'xyz',
id : 5,
}
console.log(admins.includes(user.id));
Find
It return boolean value
if it dont find anything then it return undefined
const users = [
{
name : "xyz",
id : 1
},
{
name : "abc",
id : 2
},
{
name : "pqr",
id : 3
},
];
const myUser = users.find((user) => {
if(user.id === 2){
return true
}else{
return false
}
})
console.log(myUser);
Sort
const names = ['Ram','Shyam','Gita','Babita','Sundar'];
const sortNames = names.sort();
console.log(sortNames);
Splice
it delete by index no.
const names = ['Priya','Riya','Anshu','sumit','geeta'];
let deleteName = names.splice(2,1)
console.log(names);
