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How to use the switch statement in JavaScript

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The switch statement is used to control the flow of a program and is a part of JavaScript’s conditional statements. It allows the execution of a specific code block depending upon the evaluation of an expression.

The structure of switch

  • The switch structure starts with the switch keyword followed by the expression to be evaluated in parentheses.
switch (expression){
}
  • Inside the curly braces different cases are defined followed by a value to be strictly matched with the evaluated expression.
switch (expression){
  
  case value1:
      /* implement the statement(s) to be executed when
      expression = value1 */
      break;
  case value2:
      /* implement the statement(s) to be executed when
      expression = value2 */
      break;
  case value3:
      /* implement the statement(s) to be executed when
      expression = value3 */
      break;
  default:
     /* implement the statement(s) to be executed if expression 
     doesn't match any of the above cases */ 
}
  • The break statement is used to exit the switch structure after the execution of a case. If it is not used, all the subsequent cases will be executed until the program encounters any break statement or the ending curly brace } of the structure.

  • The default: is a special type of case and is executed when none of the cases match the evaluated expression.

Example

The program will find out the day of the week based on the value of the day variable.

Let’s look at the flow chart of this example for a better understanding:

Let’s look at the implementation of the example:

var day = 2;   //change and try with different values

switch(day)
{
  case 1:      //if day = 1
    console.log("Monday");
    break;
  case 2:      //if day = 2
    console.log("Tuesday");
    break;
  case 3:      //if day = 3
    console.log("Wednesday");
    break;
  case 4:      //if day = 4
    console.log("Thursday");
    break;
  case 5:      //if day = 5
    console.log("Friday");
  case 6:      //if day = 6
    console.log("Saturday");
  case 7:      //if day = 7
    console.log("Sunday");
    break;
  default:    //if day doesn't match any of above
    console.log("Invalid");
}

RELATED TAGS

javascript
switch
conditionals
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Grokking Modern System Design Interview for Engineers & Managers

Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

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