For Loop
You should use for loop, when You know, how many times is gonna run. How many iteration’s gonna have. Use a while loop, when you don’t.
for(let i = 0; i <= 10; i++){
console.log('Number ' + i);
}
Continue statement
for(let i = 1; i <= 5; i++){
if(i === 3){
console.log('3 is my favorite number');
continue;
}
console.log('Number ' + i);
}
Number 1 Number 2 3 is my favorite number Number 4 Number 5
Break statement
for(let i = 1; i <= 5; i++){
if(i === 3){
console.log('3 is my favorite number');
continue;
}
if(i === 4){
console.log('Stop the loop');
break;
}
console.log('Number ' + i);
}
Number 1 Number 2 3 is my favorite number Stop the loop
While Loop
let i = 0;
while(i <= 10){
console.log('Number ' + i);
i++;
}
Do While Loop
It’s always gonna run at least once, no matter what.
let i = 0;
do{
console.log('Number ' + i);
i++;
}
while(i < 100);
Loop through array
For Loop
const cars = ['Ford', 'KIA', 'Toyota', 'Honda'];
for(let i = 0; i < cars.length; i++){
console.log(cars[i]);
}
Ford KIA Toyota Honda
Foreach Array Loop
cars.forEach(function(car){
console.log(car);
});
Ford KIA Toyota Honda
Access to key value pairs
cars.forEach(function(car, index){
console.log(`${index} : ${car}`);
});
0 : Ford 1 : KIA 2 : Toyota 3 : Honda
Map
We also have a method called map. It’s basically used to return different array.
const users = [
{id:1, name: 'John'},
{id:2, name: 'Jack'},
{id:3, name: 'James'}
];
const ids = users.map(function(user){
return user.id;
});
console.log(ids)
const names = users.map(function(user){
return user.name;
});
console.log(names);
For in loop – Which is often used for objects
Let’s create a single object called user
const user = {
firstName: 'John',
lastName: 'Jack',
age: 36
}
Access to key
for(let x in user){
console.log(x);
}
firstName lastName age
Access to the object with key value paris
for(let x in user){
console.log(`${x} : ${user[x]}`);
}
firstName : John lastName : Jack age : 36
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