Detailed explanation of switch statements in JavaScript: Efficiently handle multiple conditional branches

JavaScript's switch statements provide a concise way to handle multiple conditional branches, thereby avoiding lengthy if-else if-else statements. Mastering switch statements can significantly improve code efficiency and readability.

Example:

var jsLang = 'jquery';
switch (jsLang) { 
    case 'jquery': 
        alert('jQuery 勝出！');
        break;
    case 'prototype': 
        alert('prototype 勝出！');
        break;
    case 'mootools': 
        alert('mootools 勝出！');
        break;      
    case 'dojo': 
        alert('dojo 勝出！');
        break;
    default:
        alert('無(wú)人勝出！');
}
//輸出 "jQuery 勝出！"

By omitting the break statement, you can achieve the effect of "spreading through" multiple cases:

var jsLang = 'prototype';
switch (jsLang) { 
    case 'jquery': 
        alert('jQuery 不行！');
        break;
    case 'prototype': 
        alert('prototype 不行！');
    case 'mootools': 
        alert('mootools 不行！');  
    case 'dojo': 
        alert('dojo 不行！');
        break;
    default:
        alert('無(wú)人不行！');
}
//輸出 "prototype 不行！ mootools 不行！ dojo 不行！"

switch FAQs for JavaScript

switchWhat is a JavaScript

switchif-else statement is a control flow statement that allows JavaScript to execute different code blocks according to the value of a variable. It is part of the JavaScript conditional statement, and also includes the else if and switch statements. The case statement evaluates an expression and compares it to multiple cases. Once a match is found, the code block associated with the

switchJavaScript

switchcase statement first evaluates the expression once, and then compares the result with a different value of default. If a match is found, the associated code block is executed. If no match is found, the break case is performed (if present). The case keyword is used to prevent the code from accidentally running to the next case. It exits the switch block after executing the matching

switchHow to use JavaScript

switch Using the

1. switch Start with the
keyword followed by the expression in brackets.
2. case Then, write the
keyword followed by the value and colon to match the expression.
3. case Write the code to be executed if
matches the expression.
4. breakUse the caseKeyword to prevent the code from running unexpectedly to the next
.
Repeat steps 2-4 as needed.
6. default Finally, you can use the case keyword to specify if there is no
matches the expression to execute.

switchWhat is the syntax of a statement?

JavaScript switchThe syntax of the statement is as follows:

switch(表達(dá)式) {  
 case 值1:  
  // 如果表達(dá)式等于值1，則執(zhí)行的代碼  
  break;  
 case 值2:  
  // 如果表達(dá)式等于值2，則執(zhí)行的代碼  
  break;  
 ...  
 default:  
  // 如果表達(dá)式與任何case都不匹配，則執(zhí)行的代碼  
}

Expressions are evaluated only once. The value of the expression will be compared to the value of each case. If there is a match, the associated code block is executed.

Can I use JavaScript break without using switch statement?

Yes, but not recommended, as this causes the code to run unexpectedly to the next case, which is called "through". The break statement is used to prevent this from happening. It exits the case block after executing the matching switch.

JavaScript switch statements and if-else statements?

JavaScript switch statements and if-else statements is how they make decisions. The switch statement evaluates the expression once and compares it with multiple cases, executing the code block associated with the matching case. On the other hand, the if-else statement evaluates a condition, if the condition is true, one code block is executed, otherwise another code block is executed.

Can strings be used as expressions for JavaScript switch statements?

Yes, the expression in the switch statement can be any data type, including strings. The value of case must also be the same as the data type of the expression.

How to use multiple case JavaScript switch statements?

To use multiple case statements of switch, you need to write multiple switch statements in the case block. Each case statement should have a unique value that matches the expression. If the expression matches the value of case, the associated code block is executed.

Can I use JavaScript default without using switch?

Yes, but it is recommended to include default cases, as it will be executed if no case matches the expression. It acts as an alternative option.

How to use a JavaScript default statement containing a switch situation?

To use a default statement containing the switch case, you need to write the default keyword followed by a colon and if there is no case match the expression to execute. The default case does not require a break statement because it is always the last case in the switch block.

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