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
一些有趣的方法。对我来说，最好的解决方法是使用。find。
通过在find函数中使用合适的名称，可以指示多个情况是什么。
switch (varName)
{
case ["afshin", "saeed", "larry"].find(firstName => firstName === varName):
alert('Hey');
break;
default:
alert('Default case');
break;
}
其他答案更适合给定的例子，但如果你有多种情况，对我来说，这是最好的方法。
其他回答
<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>
使用switch语句的直通特性。匹配的case会一直运行，直到找到break(或者switch语句的结尾)，所以你可以这样写:
switch (varName)
{
case "afshin":
case "saeed":
case "larry":
alert('Hey');
break;
default:
alert('Default case');
}
你可以这样写:
switch (varName)
{
case "afshin":
case "saeed":
case "larry":
alert('Hey');
break;
default:
alert('Default case');
break;
}
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') }
你可以这样做:
alert([
"afshin",
"saeed",
"larry",
"sasha",
"boby",
"jhon",
"anna",
// ...
].includes(varName)? 'Hey' : 'Default case')
或者只是一行代码:
alert(["afshin", "saeed", "larry",...].includes(varName)? 'Hey' : 'Default case')
这比埃里克的回答有所改善
