TypeScript is Like C#

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Iteration ​

C# and TypeScript/JavaScript share many iteration constructs, including for, while, and do-while loops, but C# provides additional iteration mechanisms that enhance readability and safety. The classic for loop works the same in both languages, iterating with an initializer, condition, and increment (for (let i = 0; i < 10; i++) in JavaScript vs. for (int i = 0; i < 10; i++) in C#). Likewise, while and do-while loops function similarly. However, in C#, conditions must explicitly evaluate to bool, avoiding JavaScript's loose type coercion issues (e.g., while ("0") is valid in JavaScript but invalid in C#).

C# also introduces the foreach loop, which simplifies iteration over collections (foreach (var item in collection)). While JavaScript/TypeScript offers for...of for iterating over iterable objects, forEach for arrays, and for...in for object properties, C#’s foreach is more type-safe and works seamlessly with IEnumerable<T> collections, preventing off-by-one errors and ensuring safer iteration. Additionally, C#’s LINQ (Language Integrated Query) enables functional-style iteration using methods like .Select() and .Where(), offering a more declarative alternative to traditional loops—something JavaScript often achieve with array methods like .map() and .filter().

for and foreach ​

ts
for (const i = 0; i < 10; i++) {

}

for (const entry of entries) {

}
csharp
for (var i = 0; i < 10; i++) {

}

foreach (var entry in entries) {

}

for..in with JS

It is very common to mistakenly type this when switching back and forth from C# and TS. for...in and for...of have two different use cases! for...in iterates properties of the object.

while and do-while ​

ts
let count = 0

while (count < 10) {
  count++;
}

do {
  count++;
} while (count < 20);
csharp
var count = 0

while (count < 10) {
  count++;
}

do {
  count++;
} while (count < 20);

Iterators and Enumerables ​

These are broken out into their own section.