JavaScript switch

The switch is a conditional statement like if statement. Switch is useful when you want to execute one of the multiple code blocks based on the return value of a specified expression.

switch(expression or literal value){
    case 1:
        //code to be executed
      break;
    case 2:
        //code to be executed
        break;
    case n:
        //code to be executed
        break;
    default:
        //default code to be executed 
        //if none of the above case executed
}

As per the above syntax, switch statement contains an expression or literal value. An expression will return a value when evaluated. The switch can includes multiple cases where each case represents a particular value. Code under particular case will be executed when case value is equal to the return value of switch expression. If none of the cases match with switch expression value then the default case will be executed.

var a = 3;

switch (a) {
    case 1:
        alert('case 1 executed');
        break;
    case 2:
        alert("case 2 executed");
        break;
   case 3:
        alert("case 3 executed");
        break;
    case 4:
        alert("case 4 executed");
        break;
    default:
        alert("default case executed");
}

In the above example, switch statement contains a literal value as expression. So, the case that matches a literal value will be executed, case 3 in the above example.

The switch statement can also include an expression. A case that matches the result of an expression will be executed.

var a = 3;

switch (a/3) {
    case 1:
        alert("case 1 executed");
        break;
    case 2:
        alert("case 2 executed");
        break;
    case 3:
        alert("case 3 executed");
        break;
    case 4:
        alert("case 4 executed");
        break;
    default:
        alert("default case executed");
}

In the above example, switch statement includes an expression a/3, which will return 1 (because a = 3). So, case 1 will be executed in the above example.

The switch can also contain string type expression.

var str = "bill";

switch (str) 
{
    case "steve":
        alert("This is Steve");
    case "bill":
        alert("This is Bill");
        break;
    case "john":
        alert("This is John");
        break;
    default:
        alert("Unknown Person");
        break;
}

Multiple cases can be combined in a switch statement.

var a = 2;

switch (a) {
    case 1:
    case 2:
    case 3:
        alert("case 1, 2, 3 executed");
        break;
    case 4:
        alert("case 4 executed");
        break;
    default:
        alert("default case executed");
}