Edit again on 20160115

One 、window object

Dual roles

  • JS Access to the browser window interface
  • ECAMAscript Stipulated Global object

1. Global scope

All declared in global scope Variable 、 function Will become window Properties and methods of objects

delete The difference between

  • Directly in window Properties defined on objects can delete, return true
  • Global variables cannot pass through delete Operator delete ([configurable] = false), return false
  • IE<9 In the use of delete Delete window Property will throw an error

Access the difference between undeclared variables

Accessing undeclared variables throws an error , But through inquiry window Object to know whether an undeclared variable exists

oldValue; // Throw an error 
window.oldValue; // return undefined

2. Window relationships and frames (frames)

A little

3. window position

  • IE、Opera、Safari、Chrome:::

    screenLeft、screenTop

  • Firefox、Safari、Chorme:::

    screenX、screenY

Cross browser to get the position of the window relative to the left and top of the screen

var leftPos = (typeof window.screenLeft == "number") ?
window.screenLeft : window.screenX;
var topPos = (typeof window.screenTop == "number") ?
window.screenTop : window.screenY;

1

  • IE、Opera: Without browser toolbar , namely

    If window Objects are outermost objects , And the browser window is close to the top of the screen , be topPos= The height of the toolbar
  • Firefox、Safari、Chorme: Contrary to the above , With toolbar

2

  • IE、Opera: Returns the current frame Coordinates relative to the screen
  • Firefox、Safari、Chorme: Always return... For each frame in the page top.screenX and

    top.screenY value

3

  • But it is of no damn use , The above method can't get the accurate coordinate value of the window across browsers ...

Move the window

moveTo(x, y); // Parameters : New location x、y coordinate 
moveBy(x, y); // Parameters :x、y Pixels moving in the direction
  • These two methods may be disabled by the browser , stay Opera and IE 7( And higher ) The default is

    Is disabled .
  • Not for frameworks , Only for the outermost window Object use .

4. Window size ( What's the solution ?)

Get pages across browsers viewport Size

var pageWidth = window.innerWidth,
pageHeight = window.innerHeight;
if (typeof pageWidth != "number"){
if (document.compatMode == "CSS1Compat"){ // Determine the rendering mode adopted by the current browser
pageWidth = document.documentElement.clientWidth;
pageHeight = document.documentElement.clientHeight;
} else {
pageWidth = document.body.clientWidth;
pageHeight = document.body.clientHeight;
}
}

Change the window size

resizeTo();
resizeBy();
  • These two methods may be disabled by the browser , stay Opera and IE 7( And higher ) The default is

    Is disabled .
  • Not for frameworks , Only for the outermost window Object use .

5. Navigate and open windows

window.open();
// Parameters :URL、 Window target 、 Window properties 、 Whether to replace the Boolean value of history
// Returns a reference to the new window , It can be resized or moved
window.close();
// For closing window.open() Open window
top.close();
// Close the pop-up itself wroxWin.close();
alert(wroxWin.closed); // true
// After the pop-up window closes , The reference to the window is still there , Can only be used to detect its closed attribute

New window opener attribute

  • Point to open it ( call window.open()) The original window object of
  • Set to null Indicates that the new window does not need to communicate with the original window , Once the connection is cut off , Can't recover

Pop up screen program

var blocked = false;
try {
var wroxWin = window.open("http://www.wrox.com", "_blank");
if (wroxWin == null){
blocked = true;
}
} catch (ex){
blocked = true;
}
if (blocked){
alert("The popup was blocked!");
}
  • If the browser has built-in shielding program to prevent pop-up windows , be window.open() return null
  • Browser extensions or other programs block pop ups , be window.open() Throw an error

6. Timeout calls and intermittent calls 、 System dialog

A little

Two 、location object

Save current document information 、 Be able to make URL Parse into separate fragments

window.location == document.location; // true

1. Query string parameters

function getQueryStringArgs(){
// Get the query string and remove the leading question mark
var qs = (location.search.length > 0 ? location.search.substring(1) : ""),
// The object that holds the data
args = {},
// Get everything
items = qs.length ? qs.split("&") : [],
item = null,
name = null,
value = null,
// stay for Use in loop
i = 0,
len = items.length;
// Add each item to... One by one args In the object
for (i=0; i < len; i++){
item = items[i].split("=");
name = decodeURIComponent(item[0]);
value = decodeURIComponent(item[1]);
if (name.length) {
args[name] = value;
}
}
return args;
}

2. Position operation

  • Set up location.href( modify location Other properties of can also change the current page , Generate history , except hash The external pages will be replaced with new ones URL Reload )
  • location.replace("newHref") Change of position , But it doesn't generate history , You can't go back
  • location.reload() If the page doesn't change , Overload from the browser cache , To force overloading from the server, use location.reload(true). Due to network delay or system resource ,reload() Later code may not execute , So it's better to reload() On the last line of code

3、 ... and 、 navigator object

Can be used to detect browser types

Test plug-in

  • Not IE browser -plugins Array (refresh() Method )
  • IE browser -ActiveXObject type ,COM Object identifier

There is a big difference between the two methods of detecting plug-ins , A typical approach is to create a detection function for each plug-in

// Test plug-in ( stay IE Invalid in )
function hasPlugin(name){
name = name.toLowerCase();
for (var i=0; i < navigator.plugins.length; i++){
if (navigator. plugins [i].name.toLowerCase().indexOf(name) > -1){
return true;
}
}
return false;
}
// testing IE Plug in
function hasIEPlugin(name){
try {
new ActiveXObject(name);
return true;
} catch (ex){
return false;
}
}
// Detect... In all browsers Flash
function hasFlash(){
var result = hasPlugin("Flash");
if (!result){
result = hasIEPlugin("ShockwaveFlash.ShockwaveFlash");
}
return result;
}
// Detect... In all browsers QuickTime
function hasQuickTime(){
var result = hasPlugin("QuickTime");
if (!result){
result = hasIEPlugin("QuickTime.QuickTime");
}
return result;
}

Register handler

( incomprehension )

Four 、screen object

5、 ... and 、history object

Developers don't know what users have browsed URL, But it can be done without knowing history URL In this way, we can move forward and backward

go(); // Parameters : An integer value 、 character string , Passing a string jumps to the nearest position in history that contains the string 
back();
forward();

length attribute

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