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- What are the main functions of BOM and DOM
- The main function of the BOM is to provide a set of interfaces that are independent of any specific web page, allowing JavaScript programs to interact with the browser and implement various operations on the browser window. Its core is the Window object, which is the container for all global JavaScript objects. . The main function of DOM is to parse the document into an object structure, provide a set of standard programming interfaces, and enable JavaScript programs to dynamically access and modify the document content, structure and style, as well as handle browser events.
- Front-end Q&A 1593 2023-11-13 15:29:58
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- What is the difference between bom and dom
- BOM and DOM are different in terms of role and function, relationship with JavaScript, interdependence, compatibility of different browsers, and security considerations. Detailed introduction: 1. Role and function. The main function of BOM is to operate the browser window. It provides direct access and control of the browser window. The main function of DOM is to convert the web document into an object tree, allowing developers to Use this object tree to obtain and modify the elements and content of the web page; 2. Relationship with JavaScript, etc.
- Front-end Q&A 3040 2023-11-13 15:23:30
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- What is the use of regular expression boundary characters?
- The functions of regular expression boundary characters are: 1. Determine the starting position of the match and ensure that the match is performed from the beginning of the string; 2. Determine the end position of the match and specify the end position of the match; 3. Exclude specific characters to ensure that only Match independent words; 4. Precisely control the matching range; 5. Exclude the influence of escape characters to ensure that the literal meaning is matched rather than the escaped result; 6. Distinguish word boundaries, which can clarify the boundaries of words and avoid this A kind of confusion; 7. Match fixed-length strings and can accurately match fixed-length strings.
- Front-end Q&A 849 2023-11-13 15:19:42
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- What are the methods of lazy loading?
- The methods of lazy loading include lazy loading of pictures, lazy loading of videos, lazy loading of script files, lazy loading of data, etc. Detailed introduction: 1. Image lazy loading is a common lazy loading implementation method. When the page is loaded, only the images in the visible area are loaded, and the images in other areas are presented in the form of placeholders. When the user scrolls the page to The real image is loaded when the image position is specified. Image lazy loading can be achieved by using the existing JavaScript library or custom code; 2. Video lazy loading is implemented in a similar way to image lazy loading, such as when the page is loading, etc.
- Front-end Q&A 1773 2023-11-13 15:14:54
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- Why learn regular expressions
- Reasons for learning regular expressions include improving the efficiency of text processing, better understanding and utilizing existing tools and libraries, improving code readability and maintainability, solving some common text processing problems and expanding your own skills, etc. . Detailed introduction: 1. Improve the efficiency of text processing. When processing a large amount of text data, if you do not have suitable tools, you may need to manually find and replace text. Regular expressions can use concise syntax to describe the pattern to be matched, thus Quickly search and replace text; 2. Better understand and utilize existing tools and libraries, etc.
- Front-end Q&A 748 2023-11-13 15:08:02
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- What are the lazy loading frameworks?
- Lazy loading frameworks include jQuery Lazy, Echo.js, LazyLoad, Unveil.js, LazyLoadXT, etc. These lazy loading frameworks provide simple and easy-to-use APIs that can be easily integrated into existing projects. They are widely used in practical applications, especially for websites or applications that need to load a large amount of media content. By using the lazy loading framework, you can significantly increase web page loading speed, reduce bandwidth consumption, and improve user experience.
- Front-end Q&A 675 2023-11-13 14:57:43
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- What are the core objects of bom and dom
- The core objects of bom and dom are window objects and document objects respectively. The window object represents the browser window and provides a series of methods and properties to operate the browser window. The window object can be accessed and controlled through JavaScript code, and it provides some commonly used methods. The document object represents the document of the current web page. It provides a series of methods and attributes to operate the content of the web page. Through the document object, you can access and operate various elements in the web page.
- Front-end Q&A 1303 2023-11-13 14:49:06
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- What are the methods for lazy loading of images?
- Methods for lazy loading of images include lazy loading based on Intersection Observer, lazy loading using scroll event monitoring, and lazy loading using setTimeout. Detailed introduction: 1. Lazy loading based on Intersection Observer. Intersection Observer is an API provided by the browser, which can monitor whether an element enters the user's viewport; 2. Lazy loading using scroll event monitoring, which is judged by monitoring scroll events. etc.
- Front-end Q&A 1107 2023-11-13 14:41:21
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- What is the difference between front-end BOM and DOM?
- The differences are: 1. Different meanings, BOM refers to the browser object model, and DOM refers to the document object model; 2. Different structures, BOM is centered on the browser window, and the elements in the DOM document are represented as nodes and arranged in a tree shape. The structure is organized; 3. The interaction methods are different, BOM interacts with JS through the Window object, and DOM interacts through nesting and references between objects; 4. The application scope is different, BOM is used for the interaction between the browser window and the browser, DOM is used for the operation and interaction of document content; 5. Different development trends, etc.
- Front-end Q&A 2612 2023-11-13 14:36:13
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- What does the front-end new operator do?
- The front-end new operator creates a new object instance. Specific steps: 1. Create an empty simple JavaScript object; 2. Point the "__proto__" attribute of the empty object to the prototype object of the constructor; 3. Point the this keyword inside the constructor to the newly created empty object; 4. , execute the code inside the constructor, and add properties and methods to the new object; 5. If the constructor returns an object, return this object, otherwise return the newly created object, etc.
- Front-end Q&A 1405 2023-11-13 14:20:29
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- What is the function of new operator?
- The role of the new operator is to create objects, allocate memory space, inheritance, constructor execution, error handling, etc. Detailed introduction: 1. Create an object. The most common function of the new operator is to create a new object in object-oriented programming. It is implemented by calling the constructor of the object. The constructor is a special method used to initialize the object. Properties and methods, when using the new operator to create an object, the constructor will first be called, and then a reference to the newly created object will be returned; 2. Allocate memory space, the new operator will be used when creating the object, etc.
- Front-end Q&A 2109 2023-11-13 13:53:42
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- Which page routes require lazy loading?
- Page routing that requires lazy loading includes homepages, dynamically loaded pages, long list pages, content in pop-up windows or modal boxes, and pages that require user interaction. Detailed introduction: 1. The homepage is usually the first page when users visit the website, and it is also the user’s first impression of the website. Since the homepage usually contains a large amount of content and functions, such as carousels, navigation bars, recommended content, etc., If all content is loaded at once, the initial loading time will be too long; 2. Dynamically loaded pages. Dynamically loaded pages are usually based on the user's selection or input after the user performs certain operations.
- Front-end Q&A 808 2023-11-13 13:38:42
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- What is lazy loading
- Lazy loading is a common front-end optimization technique used to delay loading of resources on a page to improve the loading speed and performance of the page. Through lazy loading, the resource will only be loaded when the user needs to access it, rather than all at once. Load all resources. It can be applied to various types of resources, such as pictures, videos, etc. By rationally choosing the implementation method of lazy loading, you can improve the user experience, reduce the load on the server, and thereby improve the performance of the website.
- Front-end Q&A 1711 2023-11-13 13:16:39
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- What's wrong with implicit type conversions?
- Implicit type conversion may cause precision loss, range overflow, type safety issues, readability issues, compiler warnings and errors, logic errors, unclear code intent, performance issues, compatibility issues, testing and debugging difficulties, etc. Detailed introduction: 1. Precision loss, implicit type conversion may often lead to precision loss; 2. Range overflow, another problem caused by implicit type conversion is range overflow; 3. Type safety issues, in strongly typed programming languages In , type declaration is part of the compiler, which forces programmers to comply with type rules; 4. Readability issues, etc.
- Front-end Q&A 1519 2023-11-09 17:35:07
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- What is implicit type conversion
- Implicit type conversion refers to type conversion that occurs automatically in an expression without the need for explicit manual conversion. When we operate on values of different types, JavaScript automatically converts one data type to another. There are three type conversions in js: number conversion, string conversion and Boolean value conversion. It can simplify the code to a certain extent and make the code more flexible. It should be noted that implicit type conversion may sometimes lead to unexpected results. Therefore, when writing code, try to keep the type clear and avoid too many dependencies.
- Front-end Q&A 2693 2023-11-09 17:13:14
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