index.js

$(document).ready( function(){

$("#change-color").click(function() {
    var colors = [ 'red', 'blue', 'green', 'purple'];
    
    var randColor = colors[Math.floor(Math.random()*colors.length)];
    
    $("body").css("background-color", randColor);
});

$("#submit-name").click(function() {
    var name= $("input").val();
    $("#greeting").html("<p> Hi, "+name+"<p/p>");
});   
$("#pic1").click(function(){
    $("#gallery-main").attr("src","https://upload.wikimedia.org/wikipedia/commons/f/f9/Loxodonta_africana_-_old_bull_(Ngorongoro,_2009).jpg");
});
$("#pic2").click(function(){
    $("#gallery-main").attr("src","https://upload.wikimedia.org/wikipedia/commons/6/63/African_elephant_warning_raised_trunk.jpg");
});
$("#pic3").click(function(){
   $("#gallery-main").attr("src","https://iso.500px.com/wp-content/uploads/2014/08/2048-5.jpg");
});

});