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Examples of using switch expressions in js_javascript skills

May 16, 2016 pm 05:22 PM

switch expression

Foreword

Switch expressions are found in many languages, such as Java, C wait, and using switch is more convenient and clearer than using if else.

The usage syntax is very simple:

Copy code The code is as follows:

 
switch (n) 
{ 
case 1: 
Execute code block 1 
break; 
case 2: 
Execute code block 2 
break; 
default: 
n Code that is not executed simultaneously with case 1 and case 2
} 

The usage of various languages is basically similar.

If special mention is needed, in java 1.6 and below, the variable (n) can only be an integer. The String type is supported after Java 7.

In js, the String type can be used directly.

Usage examples

Copy code The code is as follows:

 
<!--Add by oscar999--> 
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> 
<HTML> 
 <HEAD> 
<TITLE> New Document </TITLE> 
<META NAME="Author" CONTENT="oscar999"> 
<script> 
function funcSwitch(sFlag ) 
{ 
switch(sFlag) 
{ 
case "Test1": 
alert("Test1"); 
break; 
case "Test2": 
 alert("Test2"); 
break; 
default:; 
} 
} 

funcSwitch("Test2"); 
</script> 
 </HEAD> 

<BODY> 

</BODY> 
</HTML> 

The logic is very simple and the code is very simple . Use string directly to distinguish.

The condition value corresponding to Case is also a variable

If the corresponding value after case is not a string, but a variable. This can be achieved in combination with RegExp.

Copy code The code is as follows:

 
<!--Add by oscar999--> 
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> 
<HTML> 
<HEAD> 
<TITLE> New Document &lt ;/TITLE> 
<META NAME="Author" CONTENT="oscar999"> 
<script> 
var str1 = "Test1"; 
var str2 = "Test1"; 
function funcSwitch(sFlag) 
{ 
var regExp = new RegExp(sFlag); 
switch(true) 
{ 
case regExp.test(str1): 
alert( "Test1"); 
break; 
case regExp.test(str2): 
alert("Test2"); 
break; 
default:; 
} 
} 

funcSwitch("Test1"); 

</script> 
</HEAD> 

<BODY> 

< /BODY> 
</HTML> 

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