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Table Of Contents
Mastering Node.js Web Development
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When Node.js processes a JavaScript file, it executes the statements in the order in which they have been defined. In common with most languages, JavaScript allows statements to be grouped into a function, which won’t be executed until a statement that invokes the function is executed, as shown in Listing 3.34.
Listing 3.34. Defining a function in the index.ts File in the primer Folderfunction writeValue(val: string | null) {
console.log(`Value: ${val ?? "Fallback value"}`)
}
writeValue("London");
writeValue(null);
Functions are defined with the function keyword and are given a name. If a function defines parameters, then TypeScript requires type annotations, which are used to enforce consistency in the use of the function. The function in Listing 3.34 is named writeValue, and it defines a parameter that will accept string or null values. The statement inside of the function isn’t executed until a statement that invokes...