Single-Case mode

single-case mode (Singleton)

1. limits the The number of instantiations can only be once ; (If the instance does not exist, a new instance is created; If the instance exists, a reference to that instance is returned)

2. In JavaScript, Singleton acts as a shared resource namespace, isolating code implementations from the global namespace, providing a single point of access for functions. --"JavaScript design pattern P39" (in the 1th Point of explanation)

Applicability of a single case model

1. When a class can have only one instance and the customer can access it from a well-known access point;

2. the only instance should be the subclass extensible, and the customer should be able to use an extended instance without changing the code. --"JavaScript design mode P40"

Advantages:

1. Only one time is instantiated;

2. Save memory.

Disadvantages:

1. The modules in the system appear or are tightly coupled;

2. Or its logic is too scattered;

3. It is difficult to create multiple instances;

4. testing can be difficult;

5. ~ ~ And so on.

Ideas:

1. Don't overdo it.

Application Scenarios:

1. the system does just one object to coordinate other objects time. (e.g. use in communication coordination)

Example:

• Lab 1:

• ~ ~ to be added

Learning materials:

1. the JavaScript design model;

2. Uncle Tom understands the JavaScript series in depth.

Single-Case mode