Setting up function for 'onload' more properly

public-listener-example.js

function addClickEvents() {
		//events added here to ensure all image elements fully loaded prior to adding events

		d3.select("#poster-image")	//Extinction Rebellion
			.on("mouseover", function() { showExcerpt("xr", 450, 125, "R", 500, 500, boxText); })
			.on("mouseout", function() {hideExcerpt("xr");})
			.on("click", showContrib);
		

		d3.select("#blockUpperText3")	//Robin Wall Kimmerer
			.on("mouseover", function() { showExcerpt("rk", 450, 125, "T", 500, 500, boxText); })
			.on("mouseout", function() { hideExcerpt("rk"); })
			.on("click", showContrib);

		d3.select("#blockUpperText")	//la paperson
			.on("mouseover", function() { showExcerpt("lp", 450, 125, "L", 500, 500, boxText); })
			.on("mouseout", function() { hideExcerpt("lp"); })
			.on("click", showContrib);

		d3.select("#blockBottom2")	//Tim Morton
			.on("mouseover", function() { showExcerpt("tm", 450, 125, "B", 500, 500, boxText); })
			.on("mouseout", function() { hideExcerpt("tm"); })
			.on("click", showContrib);

		d3.select("#textGreta")	//Greta Thunberg/1975
			.on("mouseover", function() { showExcerpt("gt", 450, 125, "R", 500, 500, boxText); })
			.on("mouseout", function() { hideExcerpt("gt"); })
			.on("click", showContrib);
}
document.addEventListener('DOMContentLoaded', addClickEvents );