A Function To Print Prototype Chain For A Given Object

Sometimes I get lost in prototype chain of my JavaScript objects, so I would like to have a function that would print in a friendly way the prototype chain of a given object. I am

Solution 1:

This function shows prototype chain of any object clearly:

functiontracePrototypeChainOf(object) {

    var proto = object.constructor.prototype;
    var result = '';

    while (proto) {
        result += ' -> ' + proto.constructor.name;
        proto = Object.getPrototypeOf(proto)
    }

    return result;
}

var trace = tracePrototypeChainOf(document.body)
alert(trace);

tracePrototypeChainOf(document.body) returns "-> HTMLBodyElement -> HTMLElement -> Element -> Node -> EventTarget -> Object"

Solution 2:

You could use something like the following:

functionprintPrototype(obj, i) {
    var n = Number(i || 0);
    var indent = Array(2 + n).join("-");

    for(var key in obj) {
        if(obj.hasOwnProperty(key)) {
            console.log(indent, key, ": ", obj[key]);
        }
    }

    if(obj) {
        if(Object.getPrototypeOf) {
            printPrototype(Object.getPrototypeOf(obj), n + 1);
        } elseif(obj.__proto__) {
            printPrototype(obj.__proto__, n + 1);
        }
    }
}

http://jsfiddle.net/5fv1tv1x/1/

Call it like so:

printPrototype(myObj);

It may require some modification to fit your exact needs. In node, you may also need some extra guards ( I tested in Chrome so I only needed to guard against 'obj' being undefined before recursing).

Solution 3:

functionprotoChain(o) {
    var chain = [];
    (functionprotoChainImpl(o) {
        if (o == null) {
            return;
        }
        var proto = Object.getPrototypeOf(o);
        if (proto) {
            chain.push(proto.hasOwnProperty('constructor') ? proto.constructor.name : 'undefined');
            returnprotoChainImpl(proto);
        }
    })(o);
    return chain;
}

classExampleParent {}
classExampleextendsExampleParent {}

document.write(
  'function(){}: ', protoChain(function() {}),
  '<br>',
  '[]: ', protoChain([]),
  '<br>',
  'Example: ', protoChain(newExample()),
 );