Some practical tips for JavaScript

1. Use Numberobj's ToString (radix) method to obtain a random alphanumeric character string, Radix is the cardinality of the number, is the binary, as shown below

var getrndalphanumstr = (len) + =    {var rndstr = ';      for (; rndstr.length < len; Rndstr + = Math.random (). toString (+). substr (2))    ; return rndstr.substr (0, Len);}; Getrndalphanumstr (ten)"UGYJUSOH2A"

2. Prohibit others from using the iframe form to load your Web page, as shown below

function baniframeloading () {    !== window.top.location) && (window.top.location=window.location );}

3. Floating-point rounding, using the-P and ~ ~ bit operations to do, the performance is relatively parseint better, as shown below

functionGetinteger (num) {console.time (' ~ ~ Timer ');  for(vari=0;i<num;i++){        ~~Math.random (); } console.timeend (' ~ ~ Timer '); Console.time (' |-timer ');  for(varj=0;j<num;j++) {math.random ()|; } console.timeend (' |-timer '); Console.time (' Parseint Timer ');  for(vark=0;k<num;k++) {parseint (Math.random ()); } console.timeend (' Parseint Timer ');} Getinteger (10000000)~ ~ Timer: 2608. 639ms| | Timer: 2562. 203msparseint Timer: 5111.675ms

4. Do not use the third variable to achieve the exchange of two values, as shown below

function Swap (A, b    ) {= [b,b=a][0];     return [A, b];} Console.log (Swap (10,30)); [30, 10]

5. Because the global variable undefined can be re-assigned in a function scope, resulting in some cases where an error occurs using undefined for comparison, the original undefined value needs to be obtained, as shown below

(function() {    var undefined = 1;    Console.log (undefined);}) ()void undefined gets the original----------(function() {    console.log (!! void 0);}) ()false

5. Use the Math.max method to find the maximum value of the array, as shown below

function Max (arr) {    return Math.max.apply (null, arr);}

6. Random Shuffle of array

function Arrsuffle (arr) {    return arr.sort (function() {        return Math.random () -0.5;    });} Console.log ([2,3,199,20,45]);

7. Use regular expressions to get the specified cookie

function GetCookie (ckey) {    return document.cookie.match (new RegExp (?: ^| ' + ' \\s+|; +) ' +ckey+ ' = ([^;] *) ', ' I ') [1];}

8. Quickly get the properties of an object

function Getobjkeys (obj) {    var arr = [];      for inch obj);     return arr;}

9. In the case of the front bracket, the semicolon is not automatically inserted, as shown below

var a = 1(a=1) VM2329:function(...)

　

Some practical tips for JavaScript