Jul 02, 2019

Nifty Javascript methods that will make your life easier

Ten javascript methods discussed


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The methods discussed here are of ES6+ specification, you must check if they are compatible with older versions of browsers if you want to support them or using a transpiler like Babel will be sufficient.


String.prototype.includes() / Array.prototype.includes()

includes() method checks whether a substring is present in a string, and returns true if a substring is present else it returns false. It is case-sensitive. Even array has include() method which works the same way.

const str = 'hello world'
str.includes('hello') // returns true
str.includes('Hello') // returns false

const array = [1, 2, 3, 4]
array.includes(3) // returns true

Array.prototype.every()

This method accepts a callback function as an argument. It returns true if the callback function returns a truthy value for every array element. Otherwise, false.

const array = [1, 2, 3, 4, 5]

// checks whether an element is even
function isEven(element) {
  return element % 2 === 0
}

array.every(isEven) // false

Array.prototype.some()

This method is similar to every() method, where it accepts a callback function as an argument, but returns true when the callback function returns a truthy value for any one of the array elements. Otherwise, false.

var array = [1, 2, 3, 4, 5]

// checks whether an element is even
function isEven(element) {
  return element % 2 === 0
}

array.some(isEven) // true

String.prototype.trim()

It returns a new string with whitespaces removed from both ends. Similarly, we have trimStart() and trimEnd() methods which only remove whitespaces from the start and end of the string.

var greeting = '   hello world   '
greeting.trim() // "hello world"
greeting.trimStart() // "hello world   "
greeting.trimEnd() //"   hello world"

Array.from()

The Array.from() method creates a new array from array-like objects which contain length property or iterable objects like map and set.

Array.from('hello') // [ "h", "e", "l", "l", "o" ]

const set = new Set(['foo', 'bar', 'baz', 'foo'])
Array.from(set) // [ "foo", "bar", "baz" ]

const map = new Map([
  [1, 2],
  [2, 4],
  [4, 8],
])
Array.from(map) // [[1, 2], [2, 4], [4, 8]]

Object.keys()

Returns an array of all the properties of the object

const human = {
  name: 'ABC',
  age: 30,
}

Object.keys(human) // ["name", "age"]

Object.values()

Returns an array of all the values of the object

const human = {
  name: 'ABC',
  age: 30,
}

Object.values(human) // ["ABC", 30]

Object.entries()

Returns an array with key and its value in array pair

const human = {
  name: 'ABC',
  age: 30,
}

Object.keys(human) // [["name", "ABC"], ["age", 30]]

Object.freeze()

freeze() method disables the object's properties to be modified or added or deleted.
Note: In strict mode, this results in an error if you try to modify, add or delete properties/values.

const human = {
  name: 'ABC',
  age: 30,
}

Object.freeze(human)

human.name = 'XYZ'
human.occupation = 'Developer'

console.log(human) // { name: "ABC", age: 30 }

Object.seal()

Unlike Object.freeze() method, Object.seal() allow existing properties to modified but you cannot delete or add new properties.

const human = {
  name: 'ABC',
  age: 30,
}

Object.seal(human)

human.name = 'XYZ'
human.occupation = 'Developer'

console.log(human) // { name: "XYZ", age: 30 }

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