Shadowing Practice: TypeScript in 100 Seconds - Learn English Speaking with Video

TypeScript.

Validate your JavaScript ahead of time with static type checking.

JavaScript is a dynamic language where we can do all kinds of crazy things, like reference variables that don't exist or work with objects of an unknown shape.

The code is interpreted by a browser, but if your code is broken, you won't catch it until runtime when the browser throws an error.

TypeScript prevents errors like this from ever happening by extending JavaScript with types.

The language is a strict superset of JavaScript, which means when you open up a TS file, you can write plain JavaScript with all of its extra features being completely optional.

But notice in the code here how the IDE is providing feedback about using a variable that doesn't exist.

Instead of fixing this issue weeks later in a stack trace after the company has lost millions of dollars, we can fix it right here, right now.

The reason we get this instant feedback is because TypeScript behaves like a compiled language, where JavaScript is the compilation target.

You can run the TypeScript compiler using the tsc command.

It will take the ts file and and transpile it into vanilla JavaScript.

And you can choose any flavor of JavaScript you want if you need to target ancient browsers.

And that means you can use the latest

and greatest syntax features of JavaScript without having to worry if they'll be supported in an older environment.

Your TypeScript project will likely have a tsconfig file, which provides an infinite number of ways to customize the behavior of the compiler.

But the primary goal of TypeScript is to enable static typing.

One way it achieves that is by allowing you to annotate your code with types.

We can strongly type a variable using a colon followed by its type, like a string, boolean, or number.

That's known as an explicit type.

If we then try to assign its value as the wrong type, we get an error.

Alternatively, if we set an initial value, it will implicitly infer the type.

However, there may be cases where you want to opt out of this behavior, in which case you can annotate with the any type.

That allows you to loosely type or opt out of type checking.

When working with an array, use brackets to strongly type a list.

In addition, you can define your own custom types and interfaces, which is especially powerful when working with objects.

The car interface here defines various types of the properties on an object.

We can then apply the interface to a plain JavaScript object.

The beauty of having strongly typed code is that we get autocomplete everywhere in our IDE.

We don't have to jump back and forth to documentation

or dig through stack traces to figure out why our code's not working.

If you like TypeScript as much as I do, consider becoming a pro member at Fireship.io.

For the next few days, everything will be 40% off, including lifetime memberships.

Thanks for watching, and I will see you in the next one.

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Vocabulary and speaking notes for this lesson

This C1 speaking lesson is built on the video “TypeScript in 100 Seconds”. The speaker keeps coming back to these words: type, Javascript, Typescript, code, object. This video has 33 sentences and 515 words to shadow. The speech runs for 2:24. The speaker talks fast, about 215 words per minute, so expect linked and reduced sounds. Only 77% of the words are among the 3,000 most common in English, so the vocabulary is demanding.

Key vocabulary in this video

The 15 most advanced words in the video, with pronunciation and meaning:

Word	Pronunciation	Meaning
browser noun	/ˈbɹaʊ.zəɹ/	One who or which browses.
annotate verb	/ˈæn.ə.teɪt/	To add annotation to.
compiler noun	/kəmˈpaɪlɚ/	One who compiles.
static adjective	/ˈstæt.ɪk/	Unchanging; that cannot or does not change.
stack noun	/stæk/	A large pile of hay, grain, straw, or the like, larger at the bottom than the top, sometimes covered with thatch.
autocomplete noun		A software feature that predicts the rest of a word a user is typing.
compile verb	/kəmˈpaɪl/	To make by gathering pieces from various sources.
customize verb	/ˈkʌs.tə.maɪ̯z/	To build or alter according to personal preferences or specifications.
implicitly adverb		In an implicit or implied manner.
superset noun		(symbol: ⊇) With respect to another set, a set such that each of the elements of the other set is also an element of the set.
transpile verb		Synonym of transcompile: To translate source code to a different programming language or to an older version of its original language.
validate verb	/ˈvæl.ɪ.deɪt/	To render valid.
syntax noun	/ˈsɪn.tæks/	A set of rules that govern how words are combined to form phrases and sentences.
colon noun	/ˈkoʊ.lən/	The punctuation mark ⟨:⟩.
loosely adverb	/ˈluːsli/	In a loose manner.

Phrasal verbs you will hear

Word	Meaning
figure out verb	To come to understand; to discover or find a solution; to deduce.
open up verb	To open.

Grammar in this video

The structures the speaker uses most, with the exact words from the video:

Structure	In the video
Conditional sentences if + clause, will/would + verb — a condition and its result	if your code is broken, you won't catch
Passive voice be + past participle — the focus is on what happens, not who does it	is interpreted · be supported
Relative clauses who / which + clause — extra information about a person or thing	JavaScript, which means · interfaces, which is

Pronunciation to watch

The speaker uses 5 contractions and reduced forms, such as don't, doesn't, they'll. Say them the short way, as you hear them.

The “sh” and “zh” sounds: compilation /ˌkɑm.pɪˈleɪ.ʃən/, optional /ˈɑp.ʃə.nəl/, documentation /ˌdɑkjəmɛnˈteɪʃən/
Long words — get the stress right: alternatively /ɔlˈtɝ.nə.tɪv.li/, compilation /ˌkɑm.pɪˈleɪ.ʃən/, documentation /ˌdɑkjəmɛnˈteɪʃən/

How to practise with this video

Listen to the whole video once without speaking and note the words you do not know.
Start at 0.75× speed, shadow it sentence by sentence, then go back to normal speed once it feels easy.
Record yourself and compare with the original, paying attention to words like browser, annotate, compiler.

What is the Shadowing Technique?

Shadowing is a science-backed language learning technique originally developed for professional interpreter training and popularized by polyglot Dr. Alexander Arguelles. The method is simple but powerful: you listen to native English audio and immediately repeat it out loud — like a shadow following the speaker with just a 1–2 second delay. Unlike passive listening or grammar drills, shadowing forces your brain and mouth muscles to simultaneously process and reproduce real speech patterns. Research shows it significantly improves pronunciation accuracy, intonation, rhythm, connected speech, listening comprehension, and speaking fluency — making it one of the most effective methods for IELTS Speaking preparation and real-world English communication.

Shadowing technique: read the full step-by-step guide →

Shadowing Practice: TypeScript in 100 Seconds - Learn English Speaking with Video

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Vocabulary and speaking notes for this lesson

Key vocabulary in this video

Phrasal verbs you will hear

Grammar in this video

Pronunciation to watch

How to practise with this video

What is the Shadowing Technique?