//圖片地址
let dataArr = [{
small: "./images/imgA_1.jpg",
middle: "./images/imgA_2.jpg",
big: "./images/imgA_3.jpg"
}, {
small: "./images/imgB_1.jpg",
middle: "./images/imgB_2.jpg",
big: "./images/imgB_3.jpg"
}, {
small: "./images/imgC_1.jpg",
middle: "./images/imgC_2.jpg",
big: "./images/imgC_3.jpg"
}];
let artEle = document.querySelector("article");
//拼接article的內容
let str = "";
//初始化頁面
function renderImg() {
str += `<section>
<div class="box">
<img class="middleimg" src="${dataArr[0].middle}" alt="${0}">
</div>
<div class="bigimg"></div>
</section>`;
str += `<section>
<input type="button" value="-">`;
//新增小圖片（並新增下標）
dataArr.map((item, index) => {
str += `<img src="${item.small}" alt="${index}">`
})
str += `<input type="button" value="+">
</section>`;
artEle.innerHTML = str;
//先生成在獲取節點
let bigEle = document.getElementsByClassName("bigimg")[0];
bigEle.style.backgroundImage = `url('${dataArr[0].big}')`;
}
renderImg();
//獲取小圖父節點、中圖、大圖的節點
//獲取大圖div並把它隱藏
let bigEle = document.getElementsByClassName("bigimg")[0];
bigEle.style.display = "none";
//中圖圖片
let middleimg = document.getElementsByClassName("middleimg")[0];
//大中圖包含塊
let secEle = document.getElementsByTagName("section");
//包含中圖div
let boxEle = document.getElementsByClassName("box")[0];
//生成蒙板
function meng() {
//生成蒙板節點
let asiEle = document.createElement("aside");
asiEle.className = "meng";
asiEle.style.width = (430 / 800) * 430 + "px";
asiEle.style.height = (430 / 800) * 430 + "px";
asiEle.style.backgroundImage = `url("./images/bg.png")`;
//定位
asiEle.style.position = "absolute";
asiEle.style.left = 0;
asiEle.style.top = 0;
// 蒙版隱藏
asiEle.style.display = "none";
//新增蒙板到中圖div節點
boxEle.appendChild(asiEle);
}
meng();
//點選小圖片，中圖和大圖進行更換
secEle[1].addEventListener("click", e => {
let event = e || window.event;
//獲取被點選下圖的下標
if (event.target.localName == "img") {
//大圖背景圖地址等於被點選的小圖的alt
bigEle.style.backgroundImage = `url(${dataArr[event.target.alt].big})`;
// 點選小圖時獲取小圖的alt座標等於dataArr的座標的中圖地址
middleimg.src = dataArr[event.target.alt].middle;
//點選加號或減號時判斷中途的下標
middleimg.alt = event.target.alt;
}
if (event.target.value == "+") {
//獲取當前圖片下標
let index = ++middleimg.alt;
//判斷是不是最後一張，如果是則停止
index = index >= dataArr.length - 1 ? dataArr.length - 1 : index;
// 把大圖的背景圖換成相應的圖
bigEle.style.backgroundImage = `url(${dataArr[index].big})`;
// 把中圖的背景圖換成相應的圖
middleimg.src = dataArr[index].middle;
}
if (event.target.value == "-") {
//獲取當前圖片下標
let index = --middleimg.alt;
//判斷是不是最後一張，如果是則停止
index = index <= 0 ? 0 : index;
bigEle.style.backgroundImage = `url(${dataArr[index].big})`;
middleimg.src = dataArr[index].middle;
}
});
//蒙板的顯示、隱藏、移動、大圖的移動
boxEle.addEventListener("mouseover", e => {
let mengEle = document.getElementsByClassName("meng")[0];
// 移入box顯示蒙版
mengEle.style.display = "block";
// 移入box顯示大圖
bigEle.style.display = "block";
//蒙版可移動區域
boxEle.addEventListener("mousemove", e => {
let event = e || window.event;
//滑鼠在div可移動的位置= 滑鼠在瀏覽器的位置-滑鼠在事件源的位置-滑鼠在蒙版中部
mengEle.style.left = event.clientX - boxEle.offsetLeft - mengEle.clientWidth / 2 + "px";
mengEle.style.top = event.clientY - boxEle.offsetTop - mengEle.clientHeight / 2 + "px";
//如果蒙版的移動超過或等於0，蒙版的左邊邊距為0
//讓蒙版在div內移動，但蒙版會一部分到div外面
if (parseInt(mengEle.style.left) <= 0) {
mengEle.style.left = 0;
}
//如果蒙版的移動超過或等於0，蒙版的右邊邊距為0
//讓蒙版在div內移動，但蒙版會一部分到div外面
if (parseInt(mengEle.style.top) <= 0) {
mengEle.style.top = 0;
}
//讓蒙版在div移動但不會到div外去
if (parseInt(mengEle.style.left) >= boxEle.clientWidth - mengEle.clientWidth) {
mengEle.style.left = boxEle.clientWidth - mengEle.clientWidth + "px";
}
//讓蒙版在div移動但不會到div外去
if (parseInt(mengEle.style.top) >= boxEle.clientHeight - mengEle.clientHeight) {
mengEle.style.top = boxEle.clientHeight - mengEle.clientHeight + "px";
}
bigEle.style.backgroundPositionX = -((800 / 430) * parseInt(mengEle.style.left)) + "px";
bigEle.style.backgroundPositionY = -((800 / 430) * parseInt(mengEle.style.top)) + "px";
})
//移出蒙版和大圖隱藏
boxEle.addEventListener("mouseout", e => {
mengEle.style.display = "none";
bigEle.style.display = "none";
})
})