Monkey Patching Javascript

advanced_monkeypatch.js

(function () {
    var patchedFuncts = {};
    var exportedFuncts = {};

    function generate_report(htmlElm) {
        var report = [];
        report.push("tagName",htmlElm.tagName);
        var attributes =htmlElm.attributes;
        if(attributes) {
          for(let i = 0;i < attributes.length;i++) {
              report.push(attributes[i].name,attributes[i].value);
              }
            }
        return report;
    }

    function ancestors(obj) {
        /* stolen from
        https://gist.github.com/h2non/6dd79c4312d0b20ccc4a
        */
        var hierarchy = [];
        if (['boolean', 'number', 'string', 'undefined'].indexOf(typeof obj) !== -1 || obj === null) { // primitives types
          obj = Object(obj);
        } else if (typeof obj === 'function') {
          hierarchy.push(
            obj.name ||
            (obj.toString().match(/function (\w*)/) ||
            obj.toString().match(/\[object (\w*)\]/))[1] ||
            'Anonymous Function'
          );
          obj = obj.prototype; 
        } else if (obj.toString() !== '[object Object]' && obj.prototype) { // fix Objects instances and IE issue
          hierarchy.push(
            obj.prototype.constructor.name || 
            (obj.prototype.constructor.toString().match(/function (\w*)/) || 
            obj.prototype.constructor.toString().match(/\[object (\w*)\]/))[1] || 
            'Anonymous Function'
          );
          obj = obj.prototype; 
        } else if (!Object.getPrototypeOf(obj) && obj.constructor) {
          hierarchy.push(
            obj.constructor.name || 
            (obj.constructor.toString().match(/function (\w*)/) || 
            obj.constructor.toString().match(/\[object (\w*)\]/))[1] || 
            'Anonymous Function'
          )
        }
        while (obj = Object.getPrototypeOf(obj)) {
          if (obj && obj.constructor) {
            hierarchy.push(
              obj.constructor.name || 
              (obj.constructor.toString().match(/function (\w*)/) || 
              obj.constructor.toString().match(/\[object (\w*)\]/))[1] ||
              'Anonymous Function'
            )
          }
        }
        return hierarchy
      }

    function beforeHookFunct(originalThis,name,args) {
        console.log("beforeHook : " + name);
        console.log("this : " + originalThis);
        console.log("args" + args);
    }

    function afterHookFunct(originalThis,name,args,result) {

    }

    function monkey_patch(object,methodName,beforeHook,afterHook) {
        /*
        object : to be hooked
        methodName : name of hooked method - string
        beforeHook : function which takes an array of args
        afterHook : function which takes an array of args and result
        */
        var oldFunct = object[methodName];
        var newFunct = function() {
            var originalThis = this;
            var args = Array.from(arguments);
           
            if(beforeHook) {
                beforeHook(originalThis,methodName,args);
            }
            var result = oldFunct.apply(originalThis,arguments);
           
            if(afterHook) {
                afterHook(args,result);
           }
            return result;
        }
        object[methodName] = newFunct;
    }

    // Document.prototype.createElement
    // https://developer.mozilla.org/en-US/docs/Web/API/Document/createElement
    // monkey_patch(Document.prototype,"createElement",beforeHookFunct,null);

    // Document.prototype.createDocumentFragment
    //https://developer.mozilla.org/en-US/docs/Web/API/Document/createDocumentFragment
    //monkey_patch(Document.prototype,"createDocumentFragment",beforeHookFunct,null);

    // Node.prototype.appendChild
    //https://developer.mozilla.org/en-US/docs/Web/API/Node/appendChild
    //monkey_patch(Node.prototype,"appendChild",beforeHookFunct,null);
    exportedFuncts["generate_report"] = generate_report;
    exportedFuncts["ancestors"] = ancestors;
    exportedFuncts["monkey_patch"] = monkey_patch;
    document.__monkeyFuncts = exportedFuncts;

    (function () {
        // Node.prototype.appendChild
        //https://developer.mozilla.org/en-US/docs/Web/API/Node/appendChild
        //monkey_patch(Node.prototype,"appendChild",beforeHookFunct,null);
        
        function beforeHook(originalThis,name,args) {
            //appendChild(aChild);
            var aChild = args[0];
            console.log("-----Node.appendChild(aChild)-----");
            console.log("this : " + JSON.stringify(generate_report(originalThis)));
            console.log("aChild : " + JSON.stringify(generate_report(aChild)))
            }

        monkey_patch(Node.prototype,"appendChild",beforeHook,null);
    })();
 
})()

Basic Monkey Patching.js

(function () {
    /*
    https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function
    createElement(tagName)
    createElement(tagName, options)
    https://developer.mozilla.org/en-US/docs/Web/API/Document/createElement
    */
    console.log("monkey patch start");
    var old_CreateElement = Document.prototype.createElement
    function new_CreateElement() {
        var args = Array.from(arguments);
        console.log("Document.prototype.createElement : " + args)
        return old_CreateElement.apply(this,arguments);
    }

    //Document.prototype.createElement = new_CreateElement;

    /*
    https://developer.mozilla.org/en-US/docs/Web/API/Document/createDocumentFragment
    */
    var old_CreateDocumentFragment = Document.prototype.createDocumentFragment;

    function new_CreateDocumentFragment() {
        var args = Array.from(arguments);
        console.log("Document.prototype.createDocumentFragment : " + args);
        return old_CreateDocumentFragment.apply(this,arguments);
    }

    //Document.prototype.createDocumentFragment = new_CreateDocumentFragment;

    /*
    https://developer.mozilla.org/en-US/docs/Web/API/Node/appendChild
    */

    var old_AppedNode = Node.prototype.appendChild;

    function new_AppendChild() {
        var args = Array.from(arguments);
        console.log("Node.prototype.appendChild  : " + this + " args : " + args);
        console.log("Constructor Name : " + this.constructor.name);
        return old_AppedNode.apply(this,arguments);
    }

    // Node.prototype.appendChild = new_AppendChild;

    console.log("monkey patch end")
    return true;
})();