javascript - switch范围 - js选择语句
在JavaScript中切换语句多个案例 (10)
我需要JavaScript中的switch语句中的多个案例,如:
switch (varName)
{
case "afshin", "saeed", "larry":
alert('Hey');
break;
default:
alert('Default case');
break;
}
我怎样才能做到这一点? 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。
这取决于。 Switch只评估一次。 无论情况如何,一旦匹配,所有后续的病例陈述直到“休息”为止。
var onlyMen = true;
var onlyWomen = false;
var onlyAdults = false;
(function(){
switch (true){
case onlyMen:
console.log ('onlymen');
case onlyWomen:
console.log ('onlyWomen');
case onlyAdults:
console.log ('onlyAdults');
break;
default:
console.log('default');
}
})(); // returns onlymen onlywomen onlyadults
<script src="https://getfirebug.com/firebug-lite-debug.js"></script>
你可以使用' in '操作符...
依赖于对象/哈希调用...
所以它的JavaScript一样快可以...
// 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 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]()
享受ZEE
使用switch
语句的fall-through功能。 一个匹配的情况会一直运行,直到找到一个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');
}
只需切换开关状态即可
switch (true) {
case (function(){ return true; })():
alert('true');
break;
case (function(){ return false; })():
alert('false');
break;
default:
alert('default');
}
在switch语句中执行多个case的另一种方法,当在函数内部时
function name(varName){
switch (varName) {
case 'afshin':
case 'saeed':
case 'larry':
return 'Hey';
default:
return 'Default case';
}
}
console.log(name('afshin')); //Hey
在节点中,似乎允许你这样做:
data = "10";
switch(data){
case "1": case "2": case "3": //put multiple cases on the same line to save vertical space.
console.log("small"); break;
case "10": case "11": case "12":
console.log("large"); break;
default:
console.log("strange");
break;
}
在某些情况下,这使得代码更加紧凑。
我使用这样的:
switch (sensor){
case /Pressure/g.test(sensor):{
console.log('Its pressure!');
break;
}
case /Temperature/g.test(sensor):{
console.log('Its temperature!');
break;
}
}
添加和澄清Stefano的答案,您可以使用表达式来设置切换条件的值,例如:
var i = 3
switch (i) {
case ((i>=0 && i<=5)?i:-1): console.log('0-5'); break;
case 6: console.log('6');
}
所以在你的问题中,你可以做如下的事情:
var varName = "afshin"
switch (varName) {
case (["afshin", "saeed", "larry"].indexOf(varName)+1 && varName):
console.log("hey");
break;
default:
console.log('Default case');
}
虽然没有那么多DRY ..
这适用于常规的JavaScript
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);
干杯。
<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>