Extend function - combine two functions?

Question

Now I’m in some new territory, I didn’t work with such things after a while.

What is the best way to have a Javascript class like

// In the parent instance function xyz() { var x = 1; } 

I want to set this in a class, and when the user extends the class, I want them to effectively extend this function. I know that I do not understand, but it was a long day. This is, for example, a user code.

 // In the child instance function xyz() { var y = 2; } 

The merger should result in:

 // In the merged instance function xyz() { var x = 1; var y = 2; } 

Am I smoking the wrong stuff or asking the wrong question?

Answer 1

You cannot “combine” functions as they are described, but what you can do is to redefine one function to call both yourself and the new function (before or after the original).

 var xyz = function(){ console.log('xyz'); }; var abc = function(){ console.log('abc'); }; // and, elsewhere, if you want to merge: var orig = abc; abc = function(){ orig.call(this, arguments); xyz.call(this, arguments); }; 

Inclusion (this, arguments) is not required unless you care about the execution context or if the called function is without parameters. But for clarity, I have included what you can do if you want a parameterized method.

Answer 2

You put the question in jquery, so I assume you are using jquery. with jquery you can combine objects using jQuery.extend () .

 var object1 = { apple: 0, banana: {weight: 52, price: 100}, cherry: 97 }; var object2 = { banana: {price: 200}, durian: 100 }; /* merge object2 into object1 */ $.extend(object1, object2); 

or use a prototype chain to implement inheritance. eg:

 function a() { this.t1 = 1; this.sayMyName = function() { alert('a'); } } b.prototype = new a; b.prototype.constructor = b; function b() { this.t2 = 2; this.sayMyName = function() { alert('b'); } } var obj = new b(); alert(obj.t1); // this would say 1 obj.sayMyName(); // this would say b 

Answer 3

If you understand correctly, you can try renaming the original function and calling it in a new function:

 // In the parent instance function xyz() { var x = 1; } // In the child instance var old_xyz = xyz; function xyz() { var y = 2; old_xyz(); } 

Also works with class / method inheritance:

 MyClass.prototype.old_xyz = MyClass.prototype.xyz; MyClass.prototype.xyz = function () { this.old_xyz(); } 

Answer 4

 const mergeFunctions = function () { let listOfFuncs = [] for (let func of arguments) { listOfFuncs.push(func) } return function () { for (let func of listOfFuncs) { func(arguments) } } } let x = function () { console.log("hello"); } let y = function () { console.log("world") } mergeFunctions(x, y)() ///////////////////// hello world