Expand all comments on a Facebook page

facebookExpand.js

(function(){

	'use strict';

	var digCounter = 0,
		numberOfDigTries = 3,
		bodyHeight = window.getComputedStyle(document.body).height;

	var scroll = function(){
		window.scrollBy(0, 10000);
	};

	var areWeLoading = function(){

		var loading = false;

		[].forEach.call(document.querySelectorAll(".loadingIndicator"), function(it){
			if(window.getComputedStyle(it).display !== "none"){
				loading = true;
			}
		});

		return loading;
	};

	var areWeIncreasingContent = function(){
		var retVal = false,
			currentBodyHeight = window.getComputedStyle(document.body).height;

	    if(currentBodyHeight > bodyHeight){
			retVal = true;
	    }

	    return retVal;
		
	};

	var reportDigCompleted = function(){
		alert("Done!");
	};

	var expandComments = function(){

		[].forEach.call(document.querySelectorAll(".UFIPagerLink"), function(it){
			if( !it.querySelector(".ufiPagerLoading") ){
				it.click();
			}
		});

		if( document.querySelectorAll(".UFIPagerLink").length ){
			window.setTimeout(expandComments, 3000);
		}else{

			[].forEach.call(document.querySelectorAll(".fbTimelineFeedbackComments a"), function(it){
				it.click();
			});

			window.setTimeout(reportDigCompleted, 5000);
		}

	};

	var dig = function(){

		if(digCounter > numberOfDigTries){
			expandComments();
			return;
		}

		scroll();

		if( areWeIncreasingContent() || areWeLoading() ){
			digCounter = 0;
			window.setTimeout(dig, 1000);
		}else{
			digCounter++;
			window.setTimeout(dig, 1000);
		}

	};

	dig();

}());

Kindly guide me how to use this?

I am familiar with javascript, but how to use this script?