JavaScript stepped pit (1) Keywords

Finally, enter the JavaScript part of learning
first list some common keywords, and explain the meaning of

1. var to declare variables
2. function declaration function
3. switch to select different implementation
4. break switch or termination cycle
5. return exit function
6. try ... catch statement to implement error handling block
7. do ... while executing a statement, the condition is true execute cycle
8. if ... else statement is executed according to different conditions