效果圖：
代碼：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>中介者模式 購買商品</title>
</head>
<body>
選擇顏色：
<select id="colorSelect">
<option value="">請選擇</option>
<option value="red">紅色</option>
<option value="blue">藍色</option>
</select>
選擇內存：
<select id="memorySelect">
<option value="">請選擇</option>
<option value="32G">32G</option>
<option value="16G">16G</option>
</select>
輸入購買數量：
<input type="text" id="numberInput">
您選擇了顏色：<div id="colorInfo"></div><br>
您選擇了內存：<div id="memoryInfo"></div><br>
您輸入了數量：<div id="numberInfo"></div><br>
<button id="nextBtn" disabled>請選擇手機顏色、內存和購買數量</button>
</body>
<script>
var goods = {
'red|32G': 3,
'red|16G': 0,
'blue|32G': 1,
'blue|16G': 6
}
//引入中介者
var mediator = (function(){
var colorSelect = document.getElementById('colorSelect'),
memorySelect = document.getElementById('memorySelect'),
numberInput = document.getElementById('numberInput'),
colorInfo = document.getElementById('colorInfo'),
memoryInfo = document.getElementById('memoryInfo'),
numberInfo = document.getElementById('numberInfo'),
nextBtn = document.getElementById('nextBtn');
return {
changed: function(obj){
var color = colorSelect.value,
memory = memorySelect.value,
number = numberInput.value,
stock = goods[color + '|' + memory];
if(obj == colorSelect){ //如果改變的是選擇顏色下拉框
colorInfo.innerHTML = color;
}else if(obj == memorySelect){
memoryInfo.innerHTML = memory;
}else if(obj == numberInput){
numberInfo.innerHTML = number;
}
if(!color){
nextBtn.disabled = true;
nextBtn.innerHTML = '請選擇手機顏色';
return;
}
if(!memory){
nextBtn.disabled = true;
nextBtn.innerHTML = '請選擇手機內存';
return;
}
if(!number){
nextBtn.disabled = true;
nextBtn.innerHTML = '請填寫手機數量';
return;
}
if( ( (number-0) | 0 ) !== number-0 ){ //用戶輸入的購買數量是否爲正整數
nextBtn.disabled = true;
nextBtn.innerHTML = '請輸入正確的購買數量';
return;
}
if(number > stock){ //當前選擇數量大於庫存量
nextBtn.disabled = true;
nextBtn.innerHTML = '庫存不足';
return;
}
nextBtn.disabled = false;
nextBtn.innerHTML = '放入購物車';
}
}
})()
colorSelect.onchange = function(){
mediator.changed(this)
}
memorySelect.onchange = function(){
mediator.changed(this)
}
numberInput.oninput = function(){
mediator.changed(this)
}
//以後如果想要再增加選項，如手機CPU之類的，只需在中介者對象里加上相應配置即可。
</script>
</html>