Boolean :
let isDone: boolean = false;
Number :
let decimal: number = 6;
let hex: number = 0xf00d;
let binary: number = 0b1010;
let octal: number = 0o744;
String :
let color: string = “blue”;
color = ‘red’;
*
let fullName: string = `Bob Bobbington`;
let age: number = 37;
let sentence: string = `Hello, my name is ${ fullName }.
I’ll be ${ age + 1 } years old next month.`;
*
let sentence: string = “Hello, my name is ” + fullName + “.\n\n” +
“I’ll be ” + (age + 1) + ” years old next month.”;
Array :
let list: number[] = [1, 2, 3];
The second way uses a generic array type, Array:
*
let list: Array = [1, 2, 3];
Tuple :Farklı tipleri aynı anda tutmak için aşağıdaki gibi kullanabilirsiniz.
// Declare a tuple type
let x: [string, number];
// Initialize it
x = [“hello”, 10]; // OK
// Initialize it incorrectly
x = [10, “hello”]; // Error
console.log(x[0].substring(1)); // OK
console.log(x[1].substring(1)); // Error, ‘number’ does not have ‘substring’
x[3] = “world”; // Error, Property ‘3’ does not exist on type ‘[string, number]’.
console.log(x[5].toString()); // Error, Property ‘5’ does not exist on type ‘[string, number]’.
Enum :
enum Color {Red, Green, Blue}
let c: Color = Color.Green;
*
enum Color {Red = 1, Green, Blue}
let c: Color = Color.Green;
*
enum Color {Red = 1, Green = 2, Blue = 4}
let c: Color = Color.Green;
*
enum Color {Red = 1, Green, Blue}
let colorName: string = Color[2];
console.log(colorName); // Displays ‘Green’ as its value is 2 above
Any :
let notSure: any = 4;
notSure = “maybe a string instead”;
notSure = false; // okay, definitely a boolean
*
let notSure: any = 4;
notSure.ifItExists(); // okay, ifItExists might exist at runtime
notSure.toFixed(); // okay, toFixed exists (but the compiler doesn’t check)
let prettySure: Object = 4;
prettySure.toFixed(); // Error: Property ‘toFixed’ doesn’t exist on type ‘Object’.
*
let list: any[] = [1, true, “free”];
list[1] = 100;
Void :
function warnUser(): void {
console.log(“This is my warning message”);
}
*
let unusable: void = undefined;
unusable = null; // OK if `–strictNullChecks` is not given
Null and Undefined :
// Not much else we can assign to these variables!
let u: undefined = undefined;
let n: null = null;
Never : Dönüş değeri olmayan yapılarda kullanım aşağıdaki gibidir.
// Function returning never must have unreachable end point
function error(message: string): never {
throw new Error(message);
}
*
// Inferred return type is never
function fail() {
return error(“Something failed”);
}
*
// Function returning never must have unreachable end point
function infiniteLoop(): never {
while (true) {
}
}
Object : number, string, boolean, bigint, symbol, null, undefined dışındaki tipler için kullanılabilir. Object.create şeklinde kullanımı daha uygundur.
declare function create(o: object | null): void;
create({ prop: 0 }); // OK
create(null); // OK
create(42); // Error
create(“string”); // Error
create(false); // Error
create(undefined); // Error
Type assertion :
let someValue: any = “this is a string”;
let strLength: number = (someValue).length;
*
let someValue: any = “this is a string”;
let strLength: number = (someValue as string).length;
let anahtar kelimesi JavaScript’teki var anahtar kelimesi yerine yani bir değişken tanımlarken kullanılır ancak JavaScript’teki var anahtar kelimesinden daha güvenlidir.
TypeScript değişken tanımlama örnekleri:
let orderHeaderReq: OrderHeadReq;
items: CartItemReq[];
itemCols: any[];
checkoutForm;
totalAmount: number = 0;
selectedPaymentType: number = 1;
maturities: SelectItem[];
selectedMaturity: any;]]>