js--closed functions, closures, built-in objects

Closed function: Another way of writing anonymous functions in JavaScript, creating a function that executes without naming it at the beginning

Example:

1)

(function() {    var str = ' Welcome to my home page ';    alert (str);    A+ +;}) ();

2)

! function () {    var str = ' Welcome to my homepage ';    alert (str);    A+ +;} ();

3)

~function() {    var str = ' Welcome to my homepage ';    alert (str);    A+ +;} ();

Note: Add in front of the closed function; You can avoid some unnecessary problems ~

Closures: function nesting functions, intrinsic functions can refer to parameters and variables of external functions, parameters and variables are not reclaimed by garbage collection mechanism.

Closure function:

1) A variable is stationed in memory for a long time and can be used to cycle the value of the index.

        var aLi = document.getelementsbytagname (' li ');                  for (var i=0;i<ali.length;i++)        {            (function  (i) {                     function  () {                            alert (i);                }             }) (i);        }    

2) Private variable counter, external inaccessible, avoid the pollution of global variables.

        var count = aa ();         function AA () {            var a = 1;             function BB ()            {                a++                ; return A;            }             return BB;        }        Alert (count ());        Alert (count ());

Built-in objects:

1) Document

Document.referrer//Get the address of the previous Jump page (requires server environment)

2) Location

Window.location.href//Get or reset the URL address;

Window.location.search//Get address Parameters section;

Window.location.hash//Get the page anchor point or hash value;

 <!    DOCTYPE html> window.onload  = function   () { var  Dat = Window.location.search;  var  ospan = document.getElementById (' Span01 '             var  arr = dat.split (' = '  var  a = Arr[1];        ospan.innerhtml  = A;  </script>

3) Math

Math.random//Get a random number of 0-1;

Math.floor//downward rounding;

Math.ceil//upward rounding;

js--closed functions, closures, built-in objects