JavaScript►TypeScript

TypeScript basics

! operator

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if (a!.b!.c) { }

compiles to JS:

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if (a.b.c) {
}

? operator

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let x = foo?.bar.baz();

compiles to JS:

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let x = foo === null || foo === undefined ? undefined : foo.bar.baz();

And:

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if (someObj?.bar) {
  // ...
}

is equivalent in JS to:

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if (someObj && someObj.someProperty) {
    // ...
}

TS:

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interface Content {
  getUrl?: () => string;
  url?: string;
}
interface Data {
  content?: Content;
}
let data: Data | undefined;
const url: string | undefined = data?.content?.getUrl?.();
const url2: string | undefined = data?.content?.url;