typescript default parameter
// Default Parameters
sayHello(hello: string = 'hello') {
console.log(hello);
}
sayHello(); // Prints 'hello'
sayHello('world'); // Prints 'world'typescript default parameter
// Default Parameters
sayHello(hello: string = 'hello') {
console.log(hello);
}
sayHello(); // Prints 'hello'
sayHello('world'); // Prints 'world'typescript function as parameter
function createPerson(name: string, doAction: () => void): void {
console.log(`Hi, my name is ${name}.`);
doAction(); // doAction as a function parameter.
}
// Hi, my name is Bob.
// performs doAction which is waveHands function.
createPerson('Bob', waveHands());typescript default parameter
function sayName({ first, last = 'Smith' }: {first: string; last?: string }): void {
const name = first + ' ' + last;
console.log(name);
}
sayName({ first: 'Bob' });typescript pass a function as an argunetn
class Foo {
save(callback: (n: number) => any) : void {
callback(42);
}
}
var foo = new Foo();
var strCallback = (result: string) : void => {
alert(result);
}
var numCallback = (result: number) : void => {
alert(result.toString());
}
foo.save(strCallback); // not OK
foo.save(numCallback); // OKtypescript function type
// define your parameter's type inside the parenthesis
// define your return type after the parenthesis
function sayHello(name: string): string {
console.log(`Hello, ${name}`!);
}
sayHello('Bob'); // Hello, Bob!typescript annotate return type
function add(x: number, y: number): number {
return x + y;
}Copyright © 2021 Codeinu
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