JAVASCRIPT EVENTS

    //ON CLICK
    onclick="function()";

    //ON MOUSEOVER
    onMouseOver="function()";
    <img src="img1" onMouseOver="src='img2'">
    <img src="img1" onMouseOver="this.style.color = 'green'">

    //ON FOCUS
    onFocus="function()";
    <img src="img1" onFocus="this.style.background-color = 'orange'">

    //ON BLUR (opposite to OnFocus)
    After the user un-focuses/leaves a field 
    <img src="img1" onBlur="this.style.background-color = 'orange'">

    //ON FOCUS
    <input type="button" value="Click" id="button1">
    var b1 = document.getElementById("button1");
    b1.onclick = SayHello();