XMLHTTPRquest_Interceptor.js

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<!-- @credit: EtherDream https://stackoverflow.com/users/4565883/etherdream -->

    //
    // firefox, ie8+ 
    //
    var accessor = Object.getOwnPropertyDescriptor(XMLHttpRequest.prototype, 'responseText');

    Object.defineProperty(XMLHttpRequest.prototype, 'responseText', {
    	get: function() {
    		console.log('get responseText');
    		return accessor.get.call(this);
    	},
    	set: function(str) {
    		console.log('set responseText: %s', str);
    		//return accessor.set.call(this, str);
    	},
    	configurable: true
    });

    //
    // chrome, safari (accessor == null)
    //
    var rawOpen = XMLHttpRequest.prototype.open;

    XMLHttpRequest.prototype.open = function() {
    	if (!this._hooked) {
    		this._hooked = true;
    		setupHook(this);
    	}
    	rawOpen.apply(this, arguments);
    }

    function setupHook(xhr) {
    	function getter() {
    		console.log('get responseText');

    		delete xhr.responseText;
    		var ret = xhr.responseText;
    		setup();
    		return ret;
    	}

    	function setter(str) {
    		console.log('set responseText: %s', str);
    	}

    	function setup() {
    		Object.defineProperty(xhr, 'responseText', {
    			get: getter,
    			set: setter,
    			configurable: true
    		});
    	}
    	setup();
    }

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