Frequently used array methods in JavaScript
1) concat
concat
method will merge arrays and return a new array.
example
const arr1 = [1,2,3]
const arr2 = [a,b,c]
const ans = arr1.concat(arr2)
console.log(ans) // [1,2,3,a,b,c]
- concat will return a shallow copy of an existing array
- concat can take multiple values as parameters.
const arr1 = [1,2,3] const arr2 = [a,b,c] const arr3 = [x.y,z] const ans = arr1.concat(arr2,arr3) console.log(ans) // [1,2,3,a,b,c,x,y,z]
2) find
find
will return the first element from the array which satisfy the condition.
const arr = [1,2,3,4,5]
const ans = arr.find(number => number%2 === 0)
console.log(ans) // 2
- if the condition does not match then
find
will returnundefine
- The find method executes the callback function until it satisfies the condition and will return the value on the first successful match. find with object
const obj = [
{name: "elon", company: "Tesla"},
{name:"bill", company:"Microsoft"},
{name:"jobs", company:"Apple"},
]
console.log(obj.find(()=>{name === "elon"}) //{name: "elon", company: "Tesla"}
3) some
some
will check at least one element satisfies the condition then return true
otherwise return false
const arr = ['apple', 'orange', 'mango', 'banana']
console.log(arr.some(word => word.length >= 4)) // true
console.log(arr.some(wod => word.length >= 8)) // false
- if the condition does not match then
some
will returnundefine
Some
method executes the callback function until it satisfies the condition and will return thetrue
on the first successful match.
4) map
map
will create a new array populated with the results of calling a provided function on every element in the calling array.
const arr = [10,20,30,40,50]
const ans = arr.map(number => number+5)
console.log(ans) // [15,25,35,45,55]
map
will return a new arraymap
is a pure function
const obj = [
{name: "elon", company: "Tesla"},
{name:"bill", company:"Microsoft"},
{name:"jobs", company:"Apple"},
]
const ans = obj.map(({name, company}) => ({[name]:company})
console.log(ans) // [{"elon" : "Tesla"}, {"bill":"Microsoft"},{"jobs":"Apple"}]
5) filter
filter
will create a new array with all elements which satisfies the conditions
const arr = ['apple', 'orange', 'mango', 'banana']
const ans = arr.filter(word => word.length === 5)
console.log(ans) // ['apple','mango']
const ans1 = arr.filter(word => word.length > 4)
console.log(ans1) // ['apple', 'orange', 'mango', 'banana']
filter
will return a new arrayfilter
is a pure function