Javascript: Customizing an array push based on variable - allowing standard push call for some types

Question

I am using the following technique to differentiate between copy-sourcing two different objects. The o2.copy does the deep copy while o3.copy does the shallow copy.

var o1 = {name: "old"};
console.log(o1);
var o3 = {}; var o2 = {};
o2.copy = function(o){  
    for (var key in o) {        
        o2[key] = ".."+o[key];         
    }
};

o2.copy(o1);
console.log(o2);
o3.copy = function(o){    
    o3 = o;
};
o3.copy(o1);    
console.log(o3);
o2.copy(o1);
o1.name = "New";
console.log(o2);

This works fine.

{ name: 'old' }
{ copy: [Function], name: '..old' }
{ name: 'New' }
{ copy: [Function], name: '..old' }

Now I have an array A.

 var A = [];

Now I want to bind the deep copy to the push of this array A.

Can I override the push this in such a way that if incoming arg is object, it does a deep copy else the default push? Is it possible to do this somehow?

var A = [];

A.push = function (o) {
    if (typeof o === "object") {
        A[A.length] = {} 
        for (var key in o) {        
            A[A.length-1][key] = o[key];  
        } 
    } else {
        console.log("Non-object push");
        push(); //<--- How to call the default array push here
    }
}

A.push (o1); 
A.push ("Test"); 
o1.name = "new";
console.log(A[A.length-1].name)

//current output is

{ name: 'old' }
+old
{ name: 'NewAgain' }
old
Non-object push

/temp/file.js:35
        push();
        ^
ReferenceError: push is not defined
    at Array.A.push (/temp/file.js:35:9)
    at Object.<anonymous> (/temp/file.js:40:3)
    at Module._compile (module.js:571:32)
    at Object.Module._extensions..js (module.js:580:10)
    at Module.load (module.js:488:32)
    at tryModuleLoad (module.js:447:12)
    at Function.Module._load (module.js:439:3)
    at Module.runMain (module.js:605:10)
    at run (bootstrap_node.js:418:7)
    at startup (bootstrap_node.js:139:9)

Dmitriy · Accepted Answer · 2017-04-24 10:48:05Z

1

Use .call method for a function object to get default implementation.

var A = [];

A.push = function (o) {
    if (typeof o === "object") {
        A[A.length] = {} 
        for (var key in o) {        
            A[A.length-1][key] = o[key];  
        } 
    } else {
        console.log("Non-object push");
        Array.prototype.push.call(this, o); //<--- How to call the default array push here
    }
}

answered Apr 24, 2017 at 10:48

Dmitriy

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