Ex01. for
for (let i = 0; i < 10; i++){
console.log(i);
}
for (let i = 10; i > 0; i--) {
console.log(i);
}
Ex02. for & array
const names = ['dog', 'cat', 'turtle']; //array
for(let i=0; i<names.length; i++) {
console.log(names[i]); //dog cat turtle
}
Ex03. while
let i =0;
while (i<10) {
console.log(i);
i++;
}
Ex04. Array Loop - for...of
- We don't really use this. The built-in function of Array is more useful.
let numbers = [10, 20, 30, 40, 50];
for (let number of numbers) {
console.log(number);
}
Ex05. Object Loop - entries, keys, values or for .. in
Object.entries()
Object.keys()
Object.values()
// object
const doggy = {
name : 'siru',
sound: 'bowwow',
age: 2
};
// change object into Array
console.log(Object.entries(doggy)); //[['name', 'siru'],['sound', 'bowwow'],['age', 2]]
console.log(Object.keys(doggy)); // ['name', 'sound', 'age']
console.log(Object.values(doggy)); // ['siru', 'bowwow', 2]
// object
const doggy = {
name : 'siru',
sound: 'bowwow',
age: 2
};
for(let key in doggy) {
console.log(`${key}: ${doggy[key]}`);
}
Ex06. break, continue
for (let i=0; i<10; i++) {
if ( i == 2 ) continue; // goto 'for (let i=0; i<10; i++)'
console.log(i);
if ( i == 5 ) break; // finish
}
Ex07. Practice: make sum function
// The array 'numbers'
function sumOf(numbers) {
let sum = 0;
for (let i = 0; i < numbers.length; i++) {
sum += numbers[i];
}
return sum;
}
const result = sumOf([1, 2, 3, 4, 5]);
console.log(result); //15
Ex08. Quiz : make a new array with numbers that is bigger than 3
function biggerThanThree(numbers) {
k = []
for (let number of numbers) {
if(number > 3) {
k.push(number)
}
}
return k
}
const numbers = [1, 2, 3, 4, 5, 6, 7];
console.log(biggerThanThree(numbers)); // [4, 5, 6, 7]
function biggerThanThree(numbers) {
return numbers.filter((number) => number > 3);
}
const numbers = [1, 2, 3, 4, 5, 6, 7];
console.log(biggerThanThree(numbers)); // [4, 5, 6, 7]