Summary

In this chapter, we explored the integration points that TypeScript allows when using JavaScript. We discussed how to use external JavaScript libraries or external JavaScript code within TypeScript code through the use of declaration files. We then built a declaration file from some JavaScript and learned how to describe the JavaScript types correctly for use within TypeScript. We then had a quick overview of how types are described in declaration files, and found that almost every language construct and keyword in the TypeScript language can be used within a declaration file. Finally, we took a look at how we can use some compiler options to allow both JavaScript and TypeScript files within the same project, and how TypeScript can generate declaration files for us.

In the next chapter, we will take a look at the strict compiler options that are made available to us, and how these can be used to check for potential errors within our code.