Switch as else if in JavaScript - ECMAScript 2021

In JavaScript, you can use the switch statement as an alternative to nested if-else statements. The switch statement evaluates an expression and executes the corresponding code block for the first matching case label. If there is no match for any case label, the default block is executed.

Here is the general syntax for a switch statement:

switch (expression) {
  case value1:
    // code block to execute
    break;
  case value2:
    // code block to execute
    break;
  ...
  default:
    // code block to execute if none of the cases are matched
}

Here is an example of using the switch statement to replace an if-else statement:

// using if-else statement
let num = 2;
if (num === 1) {
  console.log("One");
} else if (num === 2) {
  console.log("Two");
} else if (num === 3) {
  console.log("Three");
} else {
  console.log("Number not found");
}
// using switch statement

let num = 2;

switch (num) {

  case 1:

    console.log("One");

    break;

  case 2:

    console.log("Two");

    break;

  case 3:

    console.log("Three");

    break;

  default:

    console.log("Number not found");

}

In the above example, both the if-else statement and the switch statement will produce the same output: "Two". However, the switch statement is more concise and easier to read for larger conditions.

Here is another example of using the switch statement to handle multiple cases for a single output:

let day = 5;
switch (day) {
  case 1:
  case 2:
  case 3:
  case 4:
  case 5:
    console.log("Weekday");
    break;
  case 6:
  case 7:
    console.log("Weekend");
    break;
  default:
    console.log("Invalid day");
}

In this example, the switch statement checks if the day variable is a weekday or weekend and outputs accordingly. The use of multiple cases for a single output makes the switch statement more efficient and avoids unnecessary repetition of code.