Practical Js Tips
This is a set of practical Js tips, it could also be considered a list of Js little tricks. Although the following series of operations can make the code more concise to some extent, it will reduce readability in the absence of comments. Therefore, these black magic tricks should be used with caution.
Bitwise Operation
Integer Round
console . log ( ~ ~ ( 11.11 ) ) ; // 11
console . log ( 11.11 >> 0 ) ; // 11
console . log ( 11.11 << 0 ) ; // 11
console . log ( 11.11 | 0 ) ; // 11
console . log ( 11.11 >>> 0 ) ; // 11 // Be aware that >>> cannot be used for rounding negative numbers Odd or Even Judgment
console . log ( 7 & 1 ) ; // 1
console . log ( 8 & 1 ) ; // 0 Boolean Conversion
console . log ( ! ! 7 ) ; // true
console . log ( ! ! 0 ) ; // false
console . log ( ! ! - 1 ) ; // true
console . log ( ! ! 0.71 ) ; // true
console . log ( ! ! "" ) ; // false
console . log ( ! ! [ ] ) ; // true
console . log ( ! ! { } ) ; // true
console . log ( ! ! null ) ; // false
console . log ( ! ! undefined ) ; // false Bitwise Shift Operation
console . log ( 16 >> 1 ) ; // 8
console . log ( 16 << 2 ) ; // 64
console . log ( 1 >>> 1 ) ; // 2 Value Exchange
let a = 7 ;
let b = 1 ;
a ^= b ;
b ^= a ;
a ^= b ;
console . log ( a ) ; // 1
console . log ( b ) ; // 7
// It can also be done with arrays
b = [ a , a = b ] [ 0 ] ;
// Of course, destructuring assignment is simpler
[ a , b ] = [ b , a ] ; Determine if the Signs are the Same
let a = 1 ;
let b = 1 ;
console . log ( ( a ^ b ) >= 0 ) ; // true
console . log ( ( a ^ - b ) >= 0 ) ; // false Check if Numbers are Not Equal
let a = 111 ;
if ( a ^ 111 ) console . log ( "Not equal" ) ;
if ( a !== 111 ) console . log ( "Not equal" ) ;
if ( a ^ 11111 ) console . log ( "Not equal" ) ; // Not equal Determine if it\'s a Power of 2
const check = n => ! ( n & ( n - 1 ) ) ;
console . log ( check ( 7 ) ) ; // false
console . log ( check ( 8 ) ) ; // true Conditional Statements
let bool = true ;
if ( bool ) console . log ( 1 ) ; // 1
console . log ( bool && console . log ( 1 ) ) ; // 1 Integer Round to Nearest
const round = n => n + 0.5 * ( n > 0 ? 1 : - 1 ) | 0 ;
console . log ( round ( 0 ) ) ; // 0
console . log ( round ( 1.1 ) ) ; // 1
console . log ( round ( 1.6 ) ) ; // 2
console . log ( round ( - 1.1 ) ) ; // -1
console . log ( round ( - 1.6 ) ) ; // -2 Strings
Generate Random Strings
console . log ( Math . random ( ) . toString ( 16 ) . slice ( 2 ) ) ; // c21f331e6ce2b Repeat Strings
const repeat = ( n , str ) => Array ( n + 1 ) . join ( str ) ;
console . log ( repeat ( 5 , "ab" ) ) ; // ababababab
console . log ( "ab" . repeat ( 5 ) ) ; // ababababab // ES6 Create Links
console . log ( "Google" . link ( "www.google.com" ) ) ; // <a href="www.google.com">Google</a> Miscellaneous
Properly Handle Exceptions
try {
// something
} catch ( e ) {
window . location . href = "http://stackoverflow.com/search?q=[js]+" + e . message ;
} Elegant Way to Prove Your Excellence
console . log ( ( [ ] [ [ ] ] + [ ] ) [ + ! ! [ ] ] + ( [ ] + { } ) [ ! + [ ] + ! ! [ ] ] ) ; Operations that can substitute undefined
console . log ( void 0 ) ; // undefined
console . log ( "" . _ ) ; // undefined
console . log ( 1. . _ ) ; // undefined
console . log ( 0 [ 0 ] ) ; // undefined Substitute for Infinity
console . log ( [ - 1 / 0 , 1 / 0 ] ) ; // [-Infinity, Infinity] Clear an Array
let arr = [ 1 ] ;
arr . length = 0 ;
console . log ( arr ) ; // [] Quickly Determine if it\'s a browser below IE8
var isIE8 = ! + "1" ;
console . log ( isIE8 ) ; // false // Chrome 87 Daily Question
https://github.com/WindrunnerMax/EveryDay
Reference
https://zhuanlan.zhihu.com/p/150556186
https://zhuanlan.zhihu.com/p/262533240
https://github.com/jed/140bytes/wiki/Byte-saving-techniques
