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| <!DOCTYPE html>
<html>
<head>
<title> 事件</title>
</head>
<body>
<input type='text' id='num1' />
<select id='operate'>
<option value='+'>+</option>
<option value="-">-</option>
<option value="*">*</option>
<option value="/">/</option>
</select>
<input type='text' id='num2' />
<input type='button' value=' = ' onclick="count()" />
<input type='text' id='result' />
<script type="text/javascript">
(function count() {
/*此处写代码*/
/* calculator对象里含有以下属性：
num1:第一个输入框
num2第二个输入框
result:结果输出框
operator:运算符下拉框
btn：=按钮
option：下拉框中的每个运算符
*/
var calculator = {
num1: document.querySelector("#num1"),
num2: document.querySelector("#num2"),
result: document.querySelector("#result"),
operator: document.querySelector("#operate"),
btn: document.querySelector("input[type=button]"),
option: null,
};
// 给每个运算符命名add，subtract，multiply，divide
(function () {
calculator.option = calculator.operator.querySelectorAll("option");
calculator.option[0].setAttribute("title", "add");
calculator.option[1].setAttribute("title", "subtract");
calculator.option[2].setAttribute("title", "multiply");
calculator.option[3].setAttribute("title", "divide");
})();
// 点击=按钮时，调用operate函数，计算出结果并调用outputResult函数输出结果
calculator.btn.onclick = function () {
var index = calculator.operator.selectedIndex;//当前选中select的index
outputResult(operate(calculator.option[index].title, calculator.num1, calculator.num2));
}
// 操作函数自执行，里面的operation是算术运算，可以调用addOperation来增加运算，operate函数执行参数传递和结果运算
var operate = (function () {
var operation = {
add: function (num1, num2) {
return +num1.value + +num2.value;
},
subtract: function (num1, num2) {
return num1.value - num2.value;
},
multiply: function (num1, num2) {
return num1.value * num2.value;
},
divide: function (num1, num2) {
return num1.value / num2.value;
},
addOperation: function (name, fn) {
if (!operation[name]) {
operation[name] = fn;
}
return operation;
}
}
function operate(title) {
if (!operation[title]) throw new Error("不存在名为" + title + "的运算方法")
return operation[title].apply(operation, [].slice.call(arguments, 1, arguments.length));
}
operate.addOperation = operation.addOperation;//把operateion的addOperation方法赋予operate来给外面调用
return operate;
})();
//结果输出
function outputResult(resultNum) {
calculator.result.value = resultNum;
}
})();
</script>
</body>
</html>
|
