JavaScript switch Case Statement Learning notes

In an IF condition statement, a logical condition can only have one, and if there are multiple conditions, it can be resolved using nested IF statements, but this method increases the complexity of the program and reduces the readability of the program.

Using the switch Process Control statement can solve these problems perfectly, with the following basic structure:

Switch statement syntax

The code is as follows	Copy Code
switch (conditional expression) { Case constants: { Statement A; } Case constants: { Statement B; } Case constants: { Statement C; } ... Case constants: { Statement F; } Default { Statement N; } }

Switch statement Syntax description

Sequentially executes each statement following the case, and then executes the statement n below the default
The statements that follow each case can be multiple, but use {} to include
The values behind each case must be different.

Where A is a numeric or character type data, the value of A is A1, A2 、...... In comparison, if a is equal to one of the values, the statement following the corresponding data is executed, and when the keyword break is encountered, the program jumps out of the switch structure and executes the statement below the keyword default if a value equal to a is not found.

Switch Case statement:

The code is as follows

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var year=8; var army= "", msg= ""; Switch (parseint (year)) { Case 0: army= "Civilians"; Break Case 1: Army= "PVT"; Break Case 2: Army= "first-class soldier"; Break Case 3: Case 4: Case 5: Army= "First Class Petty Officer"; Break Case 6: Case 7: Case 8: Army= "Level two Petty officer"; Break Default if (year>8) Army= "senior Petty Officer"; } msg+= "Soldiers:" +year+ "year n"; msg+= "Conclusion:" +army; Alert (msg);

Example

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var a = 3; Switch (a) { Case 0: { document.write ("www"); } Case 1: { document.write ("Dreamdu"); } Case 2: { document.write ("com"); } Case 3: { document.write ("Www.111cn.net"); } Default { document.write ("Http://www.111cn.net"); } }

Results

Www.111cn.net
Http://www.111cn.net
Complete SWITCH statement syntax
The results above are usually not what we want, and if you execute a statement after a case, you should jump out of the switch statement, which is the true switch multiple-branch selection statement. You can add a break (jump) after each branch, and the following section describes the break.

The code is as follows	Copy Code
switch (conditional expression) { Case constants: { Statement A; } Break Case constants: { Statement B; } Break Case constants: { Statement C; } Break ... Case constants: { Statement F; } Break Default { Statement N; } }

When the value of an expression is equal to a constant following a case, the statement executed after the constant is executed, then the switch branch selection statement is executed, and the statement n after the default is performed when all the constants after the case do not conform to the expression.

Example

The code is as follows	Copy Code
var a = 3; Switch (a) { Case 0: { document.write ("www"); } Break Case 1: { document.write ("Dreamdu"); } Break Case 2: { document.write ("com"); } Break Case 3: { document.write ("Www.111cn.net"); } Break Default { document.write ("Http://www.111cn.net"); } }

Look at this function:

The code is as follows

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function Selectartiletype (typenum)//typenum is an argument passed in { Switch (typenum) { Case "0"://When typenum== "0" document.getElementById ("C_1"). style.display= "None"; document.getElementById ("c_2"). style.display= ""; Break Case "1"://When typenum== "1" document.getElementById ("C_1"). style.display= ""; document.getElementById ("c_2"). style.display= "None"; Break Case "2"://When typenum== "2" document.getElementById ("C_1"). style.display= ""; document.getElementById ("c_2"). style.display= ""; Break Default "3"://any other value document.getElementById ("C_1"). style.display= "None"; document.getElementById ("c_2"). style.display= "None"; Break } }