我需要在JavaScript开关语句的多个情况下，类似于:
switch (varName)
{
case "afshin", "saeed", "larry":
alert('Hey');
break;
default:
alert('Default case');
break;
}
我该怎么做呢?如果在JavaScript中没有办法做这样的事情，我想知道一个也遵循DRY概念的替代解决方案。
当前回答
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Example1</title>
<link rel="stylesheet" href="css/style.css" >
<script src="js/jquery-1.11.3.min.js" type="text/javascript"></script>
<script>
function display_case(){
var num = document.getElementById('number').value;
switch(num){
case (num = "1"):
document.getElementById("result").innerHTML = "You select day Sunday";
break;
case (num = "2"):
document.getElementById("result").innerHTML = "You select day Monday";
break;
case (num = "3"):
document.getElementById("result").innerHTML = "You select day Tuesday";
break;
case (num = "4"):
document.getElementById("result").innerHTML = "You select day Wednesday";
break;
case (num = "5"):
document.getElementById("result").innerHTML = "You select day Thusday";
break;
case (num = "6"):
document.getElementById("result").innerHTML = "You select day Friday";
break;
case (num = "7"):
document.getElementById("result").innerHTML = "You select day Saturday";
break;
default:
document.getElementById("result").innerHTML = "You select day Invalid Weekday";
break
}
}
</script>
</head>
<body>
<center>
<div id="error"></div>
<center>
<h2> Switch Case Example </h2>
<p>Enter a Number Between 1 to 7</p>
<input type="text" id="number" />
<button onclick="display_case();">Check</button><br />
<div id="result"><b></b></div>
</center>
</center>
</body>
其他回答
你可以使用'in'操作符… 它依赖于对象/散列调用，所以它的速度和JavaScript一样快。
// Assuming you have defined functions f(), g(a) and h(a,b)
// somewhere in your code,
// you can define them inside the object, but...
// the code becomes hard to read. I prefer it this way.
o = { f1:f, f2:g, f3:h };
// If you use "STATIC" code can do:
o['f3']( p1, p2 )
// If your code is someway "DYNAMIC", to prevent false invocations
// m brings the function/method to be invoked (f1, f2, f3)
// and you can rely on arguments[] to solve any parameter problems.
if ( m in o ) o[m]()
这在常规JavaScript中工作:
function theTest(val) {
var answer = "";
switch( val ) {
case 1: case 2: case 3:
answer = "Low";
break;
case 4: case 5: case 6:
answer = "Mid";
break;
case 7: case 8: case 9:
answer = "High";
break;
default:
answer = "Massive or Tiny?";
}
return answer;
}
theTest(9);
添加并澄清Stefano的答案，您可以使用表达式动态地设置switch中的条件值，例如:
var i = 3
switch (i) {
case ((i>=0 && i<=5) ? i : -1):
console.log('0-5');
break;
case 6: console.log('6');
}
在你的问题中，你可以这样做:
var varName = "afshin"
switch (varName) {
case (["afshin", "saeed", "larry"].indexOf(varName)+1 && varName):
console.log("hey");
break;
default:
console.log('Default case');
}
虽然很干…
在switch语句中执行多个case的另一种方法是:
函数名(varName) { switch (varName) { 例“afshin”: 例“赛义德”: 例“拉里”: 返回“嘿”; 默认值: 返回默认情况; ｝ ｝ console.log(名称(' afshin '));/ /嘿
上述方法的问题在于，每次调用具有开关的函数时，都必须重复上述几种情况。更可靠的解决方案是使用地图或字典。
这里有一个例子:
// The Map, divided by concepts var dictionary = { timePeriod: { 'month': [1, 'monthly', 'mensal', 'mês'], 'twoMonths': [2, 'two months', '2 months', 'bimestral', 'bimestre'], 'trimester': [3, 'trimesterly', 'quarterly', 'trimestral'], 'semester': [4, 'semesterly', 'semestral', 'halfyearly'], 'year': [5, 'yearly', 'annual', 'ano'] }, distance: { 'km': [1, 'kms', 'kilometre', 'kilometers', 'kilometres'], 'mile': [2, 'mi', 'miles'], 'nordicMile': [3, 'Nordic mile', 'mil (10 km)', 'Scandinavian mile'] }, fuelAmount: { 'ltr': [1, 'l', 'litre', 'Litre', 'liter', 'Liter'], 'gal (imp)': [2, 'imp gallon', 'imperial gal', 'gal (UK)'], 'gal (US)': [3, 'US gallon', 'US gal'], 'kWh': [4, 'KWH'] } }; // This function maps every input to a certain defined value function mapUnit (concept, value) { for (var key in dictionary[concept]) { if (key === value || dictionary[concept][key].indexOf(value) !== -1) { return key } } throw Error('Uknown "'+value+'" for "'+concept+'"') } // You would use it simply like this mapUnit("fuelAmount", "ltr") // => ltr mapUnit("fuelAmount", "US gal") // => gal (US) mapUnit("fuelAmount", 3) // => gal (US) mapUnit("distance", "kilometre") // => km // Now you can use the switch statement safely without the need // to repeat the combinations every time you call the switch var foo = 'monthly' switch (mapUnit ('timePeriod', foo)) { case 'month': console.log('month') break case 'twoMonths': console.log('twoMonths') break case 'trimester': console.log('trimester') break case 'semester': console.log('semester') break case 'year': console.log('year') break default: throw Error('error') }
