点击可以换图片
window.onload = function () {
var pren = document.getElementById('pren');
var cren = document.getElementById('cren');
var img = document.getElementsByTagName('img')[0];
var srt = ["../img/img1.jpg", "../img/img2.jpg", "../img/img3.jpg", "../img/img4.jpg",];
var index = 0;
pren.onclick = function () {
index--;
if (index < 0) {
index = srt.length - 1;
}
img.src = srt[index]
};
cren.onclick = function () {
index++;
if (index > srt.length - 1) {
index = 0;
}
img.src = srt[index]
};
}