Switch in TypeScript

Here’s the translated content in TypeScript, maintaining the original structure and explanations:

Switch statements express conditionals across many branches.

Here’s a basic switch.

let i = 2;
console.log("Write ", i, " as ");
switch (i) {
    case 1:
        console.log("one");
        break;
    case 2:
        console.log("two");
        break;
    case 3:
        console.log("three");
        break;
}

You can use commas to separate multiple expressions in the same case statement. We use the optional default case in this example as well.

const now = new Date();
switch (now.getDay()) {
    case 6: // Saturday
    case 0: // Sunday
        console.log("It's the weekend");
        break;
    default:
        console.log("It's a weekday");
}

switch without an expression is an alternate way to express if/else logic. Here we also show how the case expressions can be non-constants.

const t = new Date();
switch (true) {
    case t.getHours() < 12:
        console.log("It's before noon");
        break;
    default:
        console.log("It's after noon");
}

A type switch compares types instead of values. You can use this to discover the type of a variable. In this example, the variable t will have the type corresponding to its clause.

function whatAmI(i: any) {
    switch (typeof i) {
        case "boolean":
            console.log("I'm a bool");
            break;
        case "number":
            console.log("I'm an int");
            break;
        default:
            console.log(`Don't know type ${typeof i}`);
    }
}

whatAmI(true);
whatAmI(1);
whatAmI("hey");

To run the program, put the code in a file and use ts-node or compile it with tsc and use node to execute it.

$ ts-node example.ts
Write 2 as 
two
It's a weekday
It's after noon
I'm a bool
I'm an int
Don't know type string

If Else in TypeScript

Arrays in TypeScript

Learn X By Example

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Switch in TypeScript