What are the memory leaks caused by closures?

Memory leaks caused by closures include: 1. Infinite loops and recursive calls; 2. Global variables are referenced inside the closure; 3. Uncleanable objects are referenced inside the closure. Detailed introduction: 1. Infinite loops and recursive calls. When a closure refers to an external variable internally, and this closure is repeatedly called by external code, it may cause a memory leak. This is because each call will cause a memory leak in the memory. Create a new scope in the scope, and this scope will not be cleaned up by the garbage collection mechanism; 2. Global variables are referenced inside the closure, if global variables are referenced inside the closure, etc.

The operating system for this tutorial: Windows 10 system, DELL G3 computer.

Closure is an important concept in JavaScript, which allows a function to have private variables and access these private variables outside the function. However, if closures are used incorrectly, they can cause memory leak issues. The following are some common situations of memory leaks caused by closures:

1. Infinite loops and recursive calls: When a closure refers to external variables internally, and the closure is repeatedly called by external code , it may cause a memory leak. This is because each call creates a new scope in memory, and this scope is not cleaned up by the garbage collection mechanism. If this closure does not properly clean up external variables, then these variables will remain in memory until the program ends.

function outerFunction() {  
    var outerVariable = new Array(1000000).fill(0);  
    var innerFunction = function() {  
        // 这里引用了外部变量 outerVariable  
        console.log(outerVariable);  
    }  
    return innerFunction;  
}  
var leakyFunction = outerFunction();  
leakyFunction(); // 这里的调用会创建新的作用域并引用 outerVariable，导致内存泄漏

2. Global variables are referenced inside the closure: If a global variable is referenced inside the closure and the reference to the global variable is not cleared at the appropriate time, then the global variable will always exist in memory. until the program ends.

var globalVariable = new Array(1000000).fill(0);  
var closure = (function() {  
    // 这里引用了全局变量 globalVariable  
    return function() {  
        console.log(globalVariable);  
    }  
})();  
closure(); // 这里的调用会创建新的作用域并引用 globalVariable，导致内存泄漏

3. Non-cleanable objects are referenced internally in the closure: If non-cleanable objects are referenced internally in the closure (such as the closure itself, functions, DOM nodes, etc.), then these objects will always exist in memory. until the program ends.

var leakyObject = { toString: function() { return "leaky"; } };  
var closure = (function() {  
    // 这里引用了不可清理的对象 leakyObject  
    return function() {  
        console.log(leakyObject);  
    }  
})();  
closure(); // 这里的调用会创建新的作用域并引用 leakyObject，导致内存泄漏

In order to avoid memory leaks caused by closures, we need to pay attention to the following points:

Try to avoid using closures when there is no need to use them. For example, you can use static methods or classes instead of closures.

When using closures, try to avoid referencing global variables or non-cleanable objects inside the closure. If references must be made, references to them should be cleared promptly after use.

When using recursion and loops, you should ensure that each call ends at the appropriate time to avoid memory leaks caused by infinite loops and recursive calls.

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