As the front-end development, JS is the top priority. Recently, the peak of the interview has ended, and basically the offer has been settled and we are waiting for the lottery. Take this time to summarize 91 JavaScript interview questions, which are all high-frequency interview questions, hoping to be helpful to you.

Prototype chain

1.1. How many ways are there to create objects? 1.2. How does Instanceof work?

Second, the class

2.1. Class declaration? 2.2. Generate instance? Declare a class, how to generate an instance of the class?

Three, inheritance,

3.1 common points and differences between Call and apply? 3.2. How many ways to implement object inheritance/inheritance in javascript? What are the advantages and disadvantages of these ways?

4. Scope

4.1. What is your understanding of scope chains? 4.2, this? 4.3. What are the following values?

JavaScripti closures

5.1. What are the characteristics of closures? 5.2. Closure Application Scenarios? 5.3. The application of closures in actual development? 5.4. What are the following values?

Js running mechanism/single thread/asynchronous

6.1. How to understand single threading of JS? 6.2. Why is JS single threaded? 6.3. What is the difference between synchronous and asynchronous? What is an example of synchronous and asynchronous? 6.4. When is asynchrony required? 6.5. What is a task queue? 6.6. What are the following values? 6.7. What is the difference between stack and queue? 6.8. What is the difference between stack and heap? 6.9. What is an Event loop? 6.10 event – loop process? 6.11. Which statements are placed in the asynchronous task queue? 6.12. When is it put into the task queue?

Js data type

7.1. What types can BE obtained by USING Typeof for JS? 7.2. How to determine exactly if a variable is an array type? 7.3. According to the storage mode, what types of JS variables are classified and describe their characteristics? 7.4, Null and undefined? 7.5. The typical use of undefined? 7.6. Typical use of NULL? 7.7 which term is a===b in chrome60+?

Built-in functions/built-in objects in JS

8.1. What built-in functions/data encapsulate class objects in JS? 8.2. What are the built-in objects in JS? 8.3. According to the storage mode, what types of JS variables can be divided into and describe their characteristics? 8.4, Array methods/Array object methods? 8.5. Array apis? 8.6, object API?

9. Array deduplication

9.1. How can arrays be de-duplicated? (Method) 9.2, compare the speed of the above array deduplication methods? (Performance) 9.3, one sentence array deduplication? 9.4. Preserve non-repeating elements in an array? 9.5. Preserve duplicate elements in arrays?

X. JS logical judgment

10.1, can you write down the following answers?

11. Memory leaks

11.1, which operations cause memory leaks? 11.2. Solutions to JS memory leaks

Twelve, dom

12.1. What basic data structure is the DOM? 12.2. What are the common apis for DOM manipulation? 12.3. What is the difference between attributes and properties of DOM nodes? 12.4, DOM structure manipulation/common apis for how to add, remove, move, copy, create, and find nodes/DOM manipulation? 12.5. What level of DOM events? 12.6. Dom event Model? 12.7. Dom event Flow? 12.8. Describe the process of DOM event capture. 12.9. Common Applications of event objects? 12.10. Custom events/Mock events? 12.11, Generic event binding/writing a generic event listener function?

13, bom

13.1. Common attributes of bom?

Xiv. Communications

14.1. What are same-origin policies and restrictions? 14.2. How do the Front and back Ends communicate? 14.3. How many ways to communicate across domains? 14.4, the json? 14.5 Three Tags that can cross domains? 14.6. What are the usage scenarios of three cross-domain labels?

15, ajax

15.1. How do AJAX Requests work/Write an Ajax request? 15.2, the readyState? 15.3. What is the difference between Ajax asynchrony and synchronization? 15.4. What method does Ajax use to pass Chinese?

Error monitoring

16.1. Classification of front-end errors/How to detect JS errors/How to ensure your product quality? 16.2. How to catch errors? 16.3. Rationale for reporting errors?

Xvii. Modularization

17.1, Difference between AMD and CMD? 17.2, Difference between AMD and commonJs?

Virtual DOM

18.1. How to apply VDOM and what is the core API? 18.2. Conversion of the Virtual DOM to the real DOM? 18.3. Diff Implementation Process?

19. Js Foundation

19.1. What is your understanding of JS? 19.2, what is the output value of the following code? 19.4, How to distinguish array objects, ordinary objects, function objects 19.5, object-oriented, procedural 19.6, object-oriented three basic features 19.7XML and JSON difference? 19.8. Web workers and Websockets? 19.9. Javascript garbage Collection methods? 19.10. What exactly does the new operator do? 19.11. What are the ways of JS lazy loading? 19.12. What are the ways in which WEB applications actively push Data from the server to the client?

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conclusion

No matter which company interview, attach great importance to the foundation, especially for this year’s students, so the foundation must be solid before the interview. The interview is a two-way selection process, do not hold the mentality of fear to interview, is not conducive to their own play. It’s not just the salary you’re looking for, it’s whether you really like the company and whether you’re getting a real workout. In fact, I have written so much, just my own summary, not necessarily applicable to everyone, I believe that after some interviews, you will have these feelings.

In view of the above interview techniques, I also do some information to share here, hoping to better help you.