CODEWITHSUNDEEP
javascriptprototypal-inheritance
mbudnik
mbudnik

Reputation: 2107

How to call overriden methods in base constructor

Here is my code. It throws when creating new instance of inherited map (CustomMap). It seems that the init function is not available in the base constructor call when calling namespace.Map.apply(this, mapContainer);

https://jsfiddle.net/y6qg4xbn/

var namespace = window.namespace || {};

namespace.Map = function (mapContainer) {

    this.mapContainer = mapContainer;

    this.preinit();
    this.init();
}

namespace.Map.prototype.preinit = function () {
};

namespace.Map.prototype.init = function () {
};

namespace.CustomMap = function (mapContainer) {
    namespace.Map.apply(this, mapContainer);
};
namespace.CustomMap.prototype = Object.create(namespace.Map);
namespace.CustomMap.prototype.preinit = function () {
    // do some stuff or even call base preinit
}

var newMap = new namespace.Map();
var inheritedMap = new namespace.CustomMap();

Upvotes: 2

Views: 58

Answers (1)

jfriend00
jfriend00

Reputation: 707238

Change this:

namespace.CustomMap.prototype = Object.create(namespace.Map);

to this:

namespace.CustomMap.prototype = Object.create(namespace.Map.prototype);

You should base the CustomMap.prototype on the Map.prototype, not on Map. There was no .init() method in the base because you didn't include the base prototype when creating the derived prototype.

And, there's a separate problem where you need to change this:

namespace.Map.apply(this, mapContainer);

to this:

namespace.Map.call(this, mapContainer);

because mapContainer is a specific variable, not an array of arguments which means you should use .call() instead of .apply().

Upvotes: 1

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