Js function reference, memory overhead _ javascript tips-js tutorial

Function reference. For memory overhead analysis, you can refer to the following code:

The Code is as follows:

Var arr = [];
Var cc = function () {alert ('xx ');};


For (var I = 0; I <2; I ++ ){

Arr [I] = function () {alert ('yy ');}
Arr [I + 10] = cc;
}

Console. group ('start ')
Console. group ('1 ')
Console.info (arr [0] = arr [1]);
Console.info (arr [0] === arr [1]);

Console.info (arr [0]. toString ());
Console.info (arr [1]. toString ());
Console. groupEnd ('1 ')


Console. group ('2 ')
Console.info (arr [10] = arr [11]);
Console.info (arr [10] === arr [11]);

Console.info (arr [10]. toString ());
Console.info (arr [11]. toString ());
Console. group ()
Console. groupEnd ('start ');

The running result in Firefox firebug console is as follows:




Analysis:

The loop of the fifth line of code starts. After the loop ends, the arr array returns the following result:
Arr [0] = function () {alert ('yy ');}
Arr [1] = function () {alert ('yy ');}
Arr [10] = cc
Arr [11] = cc
You can see the result in the console ,.
Arr [0] is not equal to arr [1]
However, arr [10] is equal to arr [11] Because it references the previously defined variable.
Actually, in the loop process, the function () {alert ('yy');} is redefined ');}
The toString output content of arr [0] and arr [1] is the same. However, the two are independent methods that occupy their respective memory. Therefore, to save memory, functions can be defined outside the loop.
The precondition for a function to be defined outside the loop is that the function does not accept variables that change within the loop.