1. Short cycle:

Shorten the loop in one line and write less code for the loop

var names=[ 'xinyu', 'xinyuya', 'xinyuyou' ]
Original code:
for( var i=0,i<names.length;i++ ){ 
    console.log( names[i] )
}
After shortening the code:
for ( let name of names names ) console.log( name )

 

2. Adjust the length of an array

Length is not only used to get the size of the array. If we set the length of the array to any number, it will slice the array

var array1=[ 1,2,3,4,5,6 ]
var array2=[ 'xinyu','xinyuya','xinyuyou' ]
array1.length=3
array2.length=1
console.log( array1 )// [1,2,3]
console.log( array2 )// ['xinyu']

 

3. Function parameters

There is no need to define function parameters. You can use the function as an array object without declaring parameters when the function is implemented

function add( ){
    var sum=0;
    for( var i=0;i<arguments.length;i++ ){
         sum=sum+arguments[i]
    }
     console.log( 'Total Sum :',sum )// Total Sum : 9
}
add( 1,3,5 )

 

4. Timestamp in JavaScript

In JavaScript, there are many ways to use the Date method to get the Date

var date=new Date()
timetamp=date.getDate()
console.log( timetamp )

timetamp=new Date().getDate()
console.log(timetamp)

timetamp+=new Date()
console.log( timetamp )

 

5. Delete a value in the array

Usually, we use the delete method to delete an item from the array, but this is the method of punching in the array. It puts undefined on the deleted item index

You can use the splice method to do some work, but it will completely delete the index from the array without leaving any vulnerabilities

var array=[ 1,2,3,4,5 ]
delete array[4]
array.splice(4,1)
console.log( array ) // [ 1,2,3,4,5 ]

 

6. IN operator IN JavaScript

By using the IN operator, you can check whether there are keys IN the object. When you check whether there are specific keys IN the object, use the following techniques

var a=4;
var b=5;
var list={ 1；7， 3:9, 4:0, 2:9 }
console.log( a in list ) // true
console.log( b in list ) // false

 

7.JavaScript string filling

JavaScript padding is used to add padding to string text. Padding can be added at the beginning or end of a string

The following is the syntax of padStartand padEnd

padStart( targetLength,padString(optional))
padEnd( targetLength,padString(optional))

 

padString is an optional parameter in the two padding methods

The following is a code example to understand their work

console.log('123'.padStart(5)) // 123
console.log('123'.padStart(5,'0')) // 00123
console.log('123'/padEnd(5,'0')) // 12300
console.log('123'.padEnd(10,'0)) // 1230000000

 

8.Power * * operator

This feature will save a lot of mathematical calculation time. You may use math Pow() function to calculate the power of a number

But we can use the * * operator instead

Original:
var p=Math.pow( 2,5 )
console.log( p ) // 32
 Now:
var p=2**5
console.log( p ) // 32

Original:
var p = Math.pow(2,5) + Math.pow(2,5) + Math.pow(2,1) + Math.pow(2,3) + Math.pow(2,4) + Math.pow(2,9)
console.log(p) // 602
 Now: is it more concise and clear?
var p=2**5 + 2**5 + 2**1 + 2**3 + 2**4 + 2**9
console.log(p) // 602

 

9.includes()

Most people use indexOf to find elements in an array?

No,

There are better ways to do the same job,

Use the include method instead of indexOf to return a boolean result

var array=[ 'xinyu','xinyuya','xinyuyou' ]
console.log( array.includes( 'xinyuya' ) // true
console.log( array.includes( 'xin' ) // false

 

10. Redirect to URL

JavaScript has some ways to redirect to the web site in the browser after executing the code

When the user performs any action on the website and JavaScript redirects the user to another URL,

const Redirect = (url, asLink = true) => asLink ? (window.location.href = url) : window.location.replace(url);
redirect('https://medium.com/@codedev101')

 

11. Unary operator (+)

Unary operators can easily convert string numbers to numeric format and date to milliseconds

var strNum ='123.3'
var num=+strNum
console.log( num ) // 123.3
var currentDate=new Date()
var millisSince=+currentDate
console.log(millisSince)

 

12. Convert floating point numbers to integers (fast method)

To convert a floating-point number to an integer, you must use math floor()   Math.round() and math Ceil() method

You can also use the | push-pull OR operator to convert in a faster way

Original:
console.log(Math.floor(23.56))
Now:
console.log( 23.56|0 )

 

over  

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