Front end -memory management in javascript

JavaScript allocates memory when things are created and “automatically” frees it up after they don't seem to be used anymore, a process called trash pickup. Sometimes there are issues with the automated memory management which developers need to understand so as to handle them properly.

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Memory life cycle **
No matter what programming language you’re using, memory life cycle is just about always the same: Here is an outline of what happens at each step of the cycle: Allocate memory — memory is allocated by the software system which allows your program to use it. Use memory — this can be the time when your program actually makes use of the previously allocated memory. Release memory — now's the time to release the whole memory that you just don’t need in order that it can become free and available again. like the Allocate memory operation, this one is explicit in low-level languages.

What is memory?
Before jumping straight to memory in JavaScript, we’ll briefly discuss what memory is normally and the way it works in an exceedingly nutshell. A lot of things are stored during this memory: All variables and other data employed by all programs. The programs’ code, including the operating system’s. The compiler and also the software work together to require care of most of the memory management for you, but we recommend that you just take a glance at what’s occurring under the hood. When you compile your code, the compiler can examine primitive data types and calculate sooner than time what proportion of memory they'll need. The desired amount is then allocated to the program within the call stack space. The space during which these variables are allocated is named the stack space because as functions get called, their memory gets added on top of the prevailing memory. As they terminate, they're removed in an exceedingly LIFO (last-in, first-out) order.

Dynamic allocation

Unfortunately, things aren’t quite as easy after we don’t know at compile time what quantity memory a variable will need. Instead, our program has to explicitly ask the software system for the proper amount of space at run-time. This memory is assigned from the heap space. The difference between static and dynamic memory allocation is summarized within the following table: Differences between statically and dynamically allocated memory Allocation in JavaScript Now we’ll explain how the primary step (allocate memory) works in JavaScript. JavaScript relieves developers from the responsibility to handle memory allocations — JavaScript does it by itself, alongside declaring values. Some function calls end in object allocation as well.

_Using memory in JavaScript
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Using the allocated memory in JavaScript basically, means reading and writing in it. This can be done by reading or writing the worth of a variable or an object property or maybe passing an argument to a function. Release when the memory isn't needed anymore Most of the memory management issues come at this stage. The hardest task here is to work out when the allocated memory isn't needed from now on. It often requires the developer to work out where within the program such a bit of memory isn't needed anymore and free it. High-level languages embed a bit of software called refuse collector whose job is to trace memory allocation and use so as to seek out when a chunk of allocated memory isn't needed to any extent further during which case, it'll automatically free it. Most garbage collectors work by collecting memory which may not be accessed, e.g. all variables pointing thereto went out of scope. That’s, however, an under-approximation of the set of memory spaces that may be collected, because at any point a memory location should still have a variable pointing to that in scope, yet it'll never be accessed again.

Garbage collection
Due to the actual fact that finding whether some memory is “not needed anymore” is undecidable, garbage collections implement a restriction of an answer to the final problem.

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Memory references** The main concept pickup algorithms depend on is that the one among reference. In this context, the concept of an “object” is extended to something broader than regular JavaScript objects and also contains function scopes (or the worldwide lexical scope). Lexical Scoping defines how variable names are resolved in nested functions: inner functions contain the scope of parent functions whether or not the parent function has returned.

_Reference-counting pickup
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This is the only garbage pickup algorithm. An object is taken into account “garbage collectible” if there are zero references pointing thereto.
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Cycles are creating problems **
There is a limitation when it involves cycles. Within the following example, two objects are created and reference each other, thus creating a cycle. they're going to move out of scope after the call, so that they are effectively useless and will be freed. However, the reference-counting algorithm considers that since each of the 2 objects is referenced a minimum of once, neither are often garbage-collected.

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What are memory leaks?**
Just like the memory suggests, memory leaks are pieces of memory that the appliance has employed in the past but isn't needed to any extent further.

Unexpected globals is certainly a difficulty, however, more often than not your code would be infested with explicit global variables which by definition can not be collected by the rubbish collector. Special attention must run to global variables wont to temporarily store and process large bits of data. Use global variables to store data if you need to but after you do, ensure to assign it as null or reassign it once you're finished.

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The 3 common forms of common JavaScript leaks- **

1: Global variables JavaScript handles undeclared variables in a stimulating way: when an undeclared variable is referenced, a brand new variable gets created within the global object. in a very browser, the worldwide object would be window, which suggests that

2: Timers or callbacks that are forgotten setInterval for instance as it’s often employed in JavaScript.

3: Out of DOM references

Unexpected globals is certainly a difficulty, however, more often than not your code would be infested with explicit global variables which by definition can not be collected by the rubbish collector. Special attention must run to global variables wont to temporarily store and process large bits of data. Use global variables to store data if you need to but after you do, ensure to assign it as null or reassign it once you're finished.

The 3 common forms of common JavaScript leaks-

1: Global variables JavaScript handles undeclared variables in a