SOURCE

window.onload=function(){
    var p=["一","二","三","四","五"];
    var index=0;
    var timer;
    var btn1=document.getElementById("btn1");
    var btn2=document.getElementById("btn2");
    btn1.disabled=false;
    btn1.onclick=function(){
        btn1.disabled=true;
        btn2.disabled=false;
        clearInterval(timer);
        var img1=document.getElementById("img1");
        timer=setInterval(function(){
            index++;
            index=index%p.length;
            img1.alt="第"+p[index]+"张图片";
        },1000)
    };
    btn2.onclick=function(){
        btn2.disabled=true;
        btn1.disabled=false;
        clearInterval(timer);
    };
};

<img id="img1" alt="第一张图片"/><br/>
<button id="btn1" disabled="disabled">开始</button>
<button id="btn2" disabled="disabled" >停止</button>