Question 1. What is the difference between synchronous and asynchronous, try an example
Topic 2. About setTimeout
Topic 3. What are the scenarios where the front end uses asynchronous
Knowledge point
1. What is asynchronous
Result: 100 300 200
Asynchronous result: 100 300 (do not wait) 200
Synchronization result: 100 200 (waiting) 300 (will block the running of the following code)
Contrast sync
Result (sync): 100 200 (click to confirm) 300
When do you need async
1. In a situation where waiting may occur
2. During the waiting process, the program cannot be blocked like an alert.
In summary, all "await cases" need to be asynchronous
Second, the front-end uses asynchronous scenarios
3. Asynchronous and single-threaded