Throw an error when parameters required for function
const requireParam = () => {
thorw new Error('This parameter is required')
}
const sumNumbers = (val1 = requiredParam(), val2 = requiredParam()) => {
return val1 + val2
}
sumNumbers(4, 5)
//Result: 9
sumNumbers(4, null)
//Result: 4
sumNumbers(4)
//Result: Uncaught Error: This paramter is required
sumNumbers(4, undefined)
//Result: Uncaught Error: This paramter is requiredES2018 new method “finally”
fetch(https://google.com).then((response) => {
console.log(response);
}).catch((error) => {
console.log(error)
}) // es2018 finally
.finally(() => {
//your code here
})
ES5 getters and setters
const user = {
firstName: "John",
lastName: "Doe"
}
//fullname is a virtual field
get fullName(){
return this.firstName + '' + this.lastName
},
//validate age before saving
set age(value) {
if(isNaN(value)) throw Error('Age must be a number')
this._age = Number(value)
},
// get age(){
return this._age
}
console.log(user.fullName) // John Doe
user.firstName = "vignes"
console.log(user.fullName) // vignes Doe
user.age = '25'
console.log(user.age) // 25
user.age ="Invalid text" // Error: Age must be a numberMultiple conditions in an IF statement
const status = 'online';
// Classical approach
if(status === 'online' || status === 'away' || status === 'busy'){
console.log('Do Something');
}
// A better approach
if(['online', 'away', 'busy'].indexOf(status) ! === -1) {
console.log('Do Something')
}
// Check indexOf with ~ operator
if(~['online', 'away', 'busy'].indexOf(status)){
console.log('Do Something')
}
// Even Better, using includes method => Favourite
if(['online', 'away', 'busy'].includes(status)){
console.log('Do Something')
}Type coercion in Js
Type Coercion is the conversion of one type of object to a new object of a different type with similar content. Tapestry frequently must coerce objects from one type to another
console.log(false === 0) // true
console.log(true + false) // 1
console.log('val' + 40 + 60) // val4060
console.log(40 + 6 + 'val') // 46val
console.log('8' + 1) // 81
console.log('10' - 2) // 8
console.log(6 * null) // 0
ES6 startsWith() and endsWith()
const image ='hill-mountain.png';
const validImage = image.endsWith('.png');
// result: true
const hillMountain = 'Hill Mountain';
const startsWith = hillMountain.startsWith('Hill');
// result: trueArray.from()
The Array.from() methods crates a new shallowed copied array instance from an array or iterable object.
// Array from a string
Array.from('foo')
//Result: ['f', 'o', 'o']
//Array form a set
const set = new Set(['foo', 'bar', 'baz', 'foo']);
Array.from(set);
// Result get unique value: ['foo', 'bar', 'baz']
//Array from a Map
const mapper = new Map([ ['1', 'a'], ['2', 'b'] ]);
Array.from(mapper.values())
// ['a', 'b']
Array.from(mapper.keys());
//['1' , '2']
Array form an Array-like object (arguments)
function f(){
return Array.from(arguments)
}
f(1,2,3) //result [1, 2, 3]
//Using an arrow function as the map function to manipulate the elements
Array.from([1,2,3], x => x + x)
// result [2, 4 , 6]entries() method
The entries() method returns a new Array Iterator object that contains the key/ value pairs for each index in the array
const arr = ['a', 'b', 'c']
const iterator = arr.entries()
console.log(iterator.next().value)
// Result: Array [0, "a"]
console.log(iterator.next().value)
//Result: Array [1, 'b']Array replacer by JSON.stringify()
const user = {
'username': 'helperscripter',
'email': 'help@helperscript.com',
'password': 'yourpassword'
}
const userString = JSON.stirngify(user, ['username', 'email']);
//result:
{
'username': 'helperscripter',
'email': 'help@helperscript.com'
}Javascript some() and Every() functions
const moneyHeist = [
{name : 'Denvar', age: '25'},
{name : 'Oslo', age: '40'},
{name : 'Tokyo', age: '17'}
]
moneyHeist.every(el => el.age > 18)
//return false
moneyHiest.some(el => el.age < 18 )
//return true
I hope you all enjoy these methods and tricks. Thanks for reading. Please comment if it is useful.
< Javascript trick part 3
