closures in js

Concept: A closure is a function that has access to a variable in the scope of another function

1) Features of closures

• Function Nested Function
• A function can reference external parameters and variables
• Parameters and variables will not be garbage collected

2) Advantages of closures

• Variables reside in memory for long periods of time
• Avoid pollution of global variables

3) Disadvantages of closures

Variables are always kept in memory, too many closures may lead to memory leaks

4) Closure scene

• Callbacks
  In timers, event listeners, Ajax requests, cross-window communication, Web Workers, or any async, as long as you use a callback function
  , you're actually using a closure.
• Execute function immediately
• Anti-shake
  The callback is executed after n seconds after the event is triggered. If it is triggered again within these n seconds, the timer will be restarted.