javascript cookbook 2nd edition

DBecause if 2 different keys correspond to the same value, one of the 2 keys will definitely disappear for the 2 functions given by the solution.Thus the generated pseudo-inverse dictionary length will be shorter than the original dictionary length, in any case, only if the value in D is hashed, then the previous function will work properly, otherwise the function would give a TypeError exceptionThis function obtains the Iteritems method to generate a pair of keys and other corresponding values

/* Progressive enhancement smooth degraded web page structure layer (structural layer): HTML presentation layer (presentation layer): CSS JavaScript-javascript DOM Programming Art (2nd edition)

Compression script:The so-called compression script, refers to the script file unnecessary bytes, such as spaces and comments, all deleted, so as to achieve the purpose of "compressed" file. Fortunately, there are many tools that can do it for you. Some refiners will even rewrite some of your code, using shorter variable names to reduce the overall file size. The streamlined code, while not easy to read, can drastically reduce file size. In most cases, you should have two versions, one working

which are contained in the array returned by the ChildNodes property.However, each node has a NodeType property. The NodeType attribute has a total of 12 desirable values, but only 3 of them have value: The NodeType attribute value of the element node is 1, the property node's NodeType property value is 2, and the NodeType property value of the text node is 3.If you want to change the value of a text node, use the NodeValue property provided by the DOM.Array element Childnodes[0] There is a mor

October 1998, and this standardized DOM allows any programming language to be used for any document written in any one of the markup languages. Control.1.4.1 Outside of browser considerationsThe DOM is an API (application programming Interface, application programming Interface) and is a basic agreement that has been recognized by all parties concerned.The definition of the DOM is: "An interface that is independent of the system platform and programming language , where programs and scripts c

Objective:Although it is almost a load, but still on their own occupation-the front-end, vague, muddle. Therefore, does not seek the crane to stand alone group, but knows. From the JavaScript DOM Programming Art (2nd edition), start with a foundation, and at the same time, understand the history of industry development. More unknown so the insistence, less a trac

not parsed correctly when the semicolon is missing.Generally speaking, if a statement starts with a "(", "[", "/", "+" or "-", it is most likely to be parsed together with the previous statement.Some programmers prefer to keep a semicolon in front of the statement so that even if the previous statement is modified and the semicolon is mistakenly deleted, the current statement will parse correctly. But there are two exceptions.The first exception is that there can be no line breaks between retur

, this usage is not a good habit and is not recommended for everyone to use. Essentially, when you create an associative array, you create an array object's properties. In JavaScript, all variables are actually objects of some kind. For example, a Boolean value is an object of type Boolean. In the above example, you are actually adding the name, year, and living three properties to the lemon array. Ideally, you should not modify the properties of an a

adept at handling repetitive tasks. It is easy to traverse a long list with a while or for loop.Responding to EventsCSS provides: pseudo-class attributes such as hover allow us to change the style based on the state of the HTML element. The DOM can also respond to changes in the state of an HTML element through events such as onmouseover. So when to use: hover, when to use onmouseover?The simplest answer is to choose the easiest way to achieve it. For example, if you just want the link to chang

JavaScript and DOM, we can completely collect that information and insert it into the document using the SUP element.List of shortcut keysThe AccessKey property can associate an element (such as a link) with a specific key on the keyboard. This is useful for people who can't or don't like using a mouse to browse the Web.In general, in browsers for Windows systems, the use of shortcut keys is to press the ALT key and specific keys at the same time on

=document.getelementbyid (' id name '); Returns the element node, where each element node is an object, so the data type returned is an objectThe tag and class methods can iterate through a set of elements with a for loop4, gets and sets the element's attributes , which belong to the element node objectGets the property name of the attribute getattribute, a parameter that needs to be obtained.Set the property SetAttribute, two parameters, need to modify the property name, the modified value.Note

() { if(document.getElementById) { statements using getElementById }} Although it is a simple if statement, it ensures that the "old" browsers do not cause problems with my scripting code, so that the script has good backwards compatibility.Browser sniffing technology: addresses backward compatibility issues by extracting information from a browser vendor.Performance considerations: Determining the optimal performance of script execution1. Minimize access to the DOM and minimize markup2. M

syntax does not allow a variable name to contain spaces or punctuation (the dollar sign "$" exception)JavaScript variable names are allowed to contain letters, numbers, dollar signs, and underscores (but the first character is not allowed to be a number)Hump format naming:Remove Middle white space (underline), followed by each new word start with uppercase letters Script > var ="happy"; Script >Usually the hump format is the preferred format for

page content asynchronously.With Ajax, you can only update a small part of the page. Other content-logo, navigation, head, foot, no reload.The main advantage of Ajax is that requests to the page are sent asynchronously to the server. The server does not respond to the request with the entire page, it processes the request in the background, while the user continues to browse the page and interact with the page. Your script can load and create page content on demand without interrupting the user

1. A document is a tree of nodes2. Nodes are divided into different types: element nodes, text nodes, attribute nodes, etc.3. Each node is an object, and the atom of the DOM is an element node4.getElementById returns an object that corresponds to a specific element node in the document5.getELementsByTagName and Getelementsbyclassname return an array of objects that correspond to a specific set of ELEMENT nodes in the document, respectively.The 6.typeof operator can tell us whether its operand is

False2. Range of valuesDue to memory limitations, ECMAScript cannot save all the values in the world, and the smallest value ECMAScript can represent is saved in Number.min_value, which is 5e-324 in most browsers. The maximum value that can be represented is saved in Number.MAX_VALUE, which is 1.7976931348623157e+308 in most browsers. If the result of a calculation is given a value that is outside the range of JavaScript values, if the value is negat

Doe // Script Error　(2) All variables that do not have a direct assignment defined are automatically declared as having global scopefunction dosomething () { var Name= "Zhang San"; NewName= "John Doe"; // Zhang San // John Doe // Script ErrorThe variable blogname has a global scope, and AuthorName cannot be accessed outside the function.(3) All Window object properties have global scopeIn general, the built-in properties of the Window object have global scope, such as Window.name, Win

never be able to leave the current link.What about those people who use keyboards only?Fortunately, the OnClick event handler is smarter than we thought. Although its name "onclick" gives the impression that it is only associated with a mouse click action, it is not true: in almost all browsers, the action of tabbing to a link and pressing ENTER will also trigger the OnClick event.It is best not to use the OnKeyPress event handler function. The OnClick event handler function has been able to me

JavaScript code must be executed through the html/xhtml document, and the first way is to put the JS code between the to put the , allowing the browser to load the page fasterPS: Browser page load order: Please read this articleJS Note: 1,///2,/* 3, JS can be used JS allows programmers to directly assign values to variables without prior declaration, the most efficient declaration and assignment practices: var mood= "Happy", age=33;JS is a weakly typ

The Style property is an object and can only return inline styles.When you need to reference a CSS property with a minus sign in the middle, the DOM asks for the hump naming method, that is, the CSS property font-family becomes the DOM attribute fontFamliy:element.style.fontFamilyRegardless of the number of hyphens in the CSS style attribute's name, the DOM is all represented by the Hump naming method, which is the CSS property backg-color corresponding to the DOM attribute backgroundcolor.CSS3