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Javascript Array methods used in my work

Web developer in Longbridge
・2 min read

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Here list some Javascript Array methods witch helpful and useful to my work

some & every

let users = [{name: 'foo',age: 18},{name: 'bar',age: 21}]
users.some((user)=>user.age < 20) // true
users.every((user)=>user.age < 20) // false
  • some just return true if users has one user age < 20
  • every just return true if all users age < 20


// splice(index[, deleteCount, elem1, ..., elemN])
const fruits = ['apple','pera','grape']
fruits.splice(1,1,'pineapple','watermelon') // ['pera']
// fruits: ['apple','pineapple','watermelon','grape']

splice method will return modified array elements but will mutation origin array. fruits will be ['apple','pineapple','watermelon','grape']


  • index which started index you will mutation
  • deleteCount will declare how many element you will replaced
  • elem1,...eleN will after index poistion

unshift & push

const fruits = ['apple','pera','grape']

fruits.unshift(...['pineapple']) // will return fruits length 4
console.log(fruits) // (4) ["pineapple", "apple", "pera", "grape"]

fruits.push('watermelon')  // will return fruits length 5
console.log(fruits) //(5) ["pineapple", "apple", "pera", "grape", "watermelon"]
  • unshfit(...item) will push item to beginning of array
  • push(item) will push item to end of array


["foo", "bar", "zzzzz"].forEach((item, index, array) => {
  console.log(`${item} is at index ${index} in ${array}`);

Usual we just pass first two args item, index but array used when you need referer the iterate object here is ["foo", "bar", "zzzzz"]

find & findIndex

const fruits = ['apple','pera','grape']

fruits.find((fruit)=> fruit==='apple') // apple
fruits.findIndex((fruit)=> fruit==='grape') // 2

// if not found will return -1
fruits.findIndex((fruit)=> fruit==='notfound') // -1
  • find will return the first matched element in fruits
  • findIndex will return the first matched element index at fruits array


const fruits = ['apple','pera','grape']
let results = fruits.filter((fruit) => fruit.length > 4) // (2) ["apple", "grape"]

fileter will return new array witch iterate callback return true


let items = ["foo", "bar", "zzz"].map(item => `lol:${item}`);
console.log(items); // (3) ["lol:foo", "lol:bar", "lol:zzz"]

We can use map transform array element and return new array

Not limited to the above method aslo includes: reverse, reduce, concat ,slice , join

Hope it can help you :)

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