Hook Javascript Function

In the document upgrade scheme, because a new template is used, I need to perform some checks before the original system executes some functions. If it is set up, the original function is executed. Otherwise, my new logic is executed, then, determine whether to execute the original function based on the actual situation.

We know that Javascript Functions include static functions, member functions, and member functions of instantiated objects. The implementation of these functions is differentiated between normal functions and anonymous functions. So when we Hook members, we need to pay attention to these situations.

For example, if you call a Hook with the following function, the following output is expected:

// The global function has no parameters.

Function Method1 (){

Alert ('method1 ');

}

 

Method1.hook (function ()

{

Alert ('befor Method1 ');

Return true;

},

Function ()

{

Alert ('after Method1 ');

}

);

 

Method1 ();

/* Output

Befor Method1

Method1

After Method1

*/

Alert ('-----------------');

// Global functions have Parameters

Function Method2 (name ){

Alert ('method2 with '+ name );

}

Method2.hook (function (name)

{

Alert ('befor Method2 with '+ name );

Return true;

},

Function ()

{

Alert ('after Method2 ');

}

);

Method2 ('evlon ');

/* Output

Befor Method2 with evlon

Method2 with evlon

After Method2

*/

 

Alert ('-----------------');

 

// Hook the toString Function

String. prototype. toString. hook (String. prototype, function ()

{

Alert ('befor string. tostring ');

Return true;

});

 

Var s = "return s ";

Alert (s. toString ());

/* Output

Befor string. toString

Return s

*/

Alert ('-----------------');

 

 

// Hook the system's existing global function parseInt

ParseInt. hook (function ()

{

Alert ('befor parseint ');

Return true;

});

 

Alert (parseInt ('5 '));

/* Output

Befor parseInt

5

*/

Alert ('-----------------');

 

// Hook the join method for all array objects

Array. prototype. join. hook (Array. prototype, function (span)

{

Alert ('befor Array. prototype. join separator' + span );

Return true;

});

 

Alert ([3, 5, 6]. join (','));

/* Output

Befor Array. prototype. join separator,

3, 5, 6

*/

Alert ('-----------------');

 

Var list = [3, 5, 6];

// Hook list the join method of the Instance array object

List. join. hook (list, function (span)

{

Alert ('befor list. join separator' + span );

Return true;

});

 

Alert (list. join (','));

/* Output

Befor list. join separator,

Befor Array. prototype. join separator,

3, 5, 6

*/

Alert ('-----------------');

 

 

Var list2 = [3, 5, 6, 7];

// This call will not generate befor list. join separator,

Alert (list2.join (','));

 

/* Output

Befor Array. prototype. join separator,

3, 5, 6, 7

*/

Alert ('-----------------');

// Custom class

Function People (){

// Member functions with Parameters

This. getName = function (name ){

Alert ('in getName with '+ name );

Return 'Return evlon ';

}

 

}

 

Var p = new People ();

Var p2 = new People ();

 

// Here we only Hook the function call of instance p2

P2.getName. hook (p2, 'getname2 ',

Function (name ){

Alert ('befor getName2 with '+ name );

Return true;

},

Function (){

Alert ('after getname2 ');

}

);

P2.getName. hook (p2,

Function (name ){

Alert ('befor getName with '+ name );

Return true;

},

Function (){

Alert ('after getname ');

}

);

 

// Because only P2 is hooked, this call is not affected.

Alert (p. getName ('argname '));

/* Output

In getName with argName

Return evlon

*/

Alert ('-----------------');

 

Alert (p2.getName ('argname '));

/* Output

Befor getName with argName

In getName with argName

After getName

Return evlon

*/

 

Alert ('-----------------');

Alert (p2.getName2 ('argname2 '));

/* Output

Befor getName2 with argName2

In getName with argName2

After getName2

Return evlon

*/

 

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