For loop in TypeScript

TypeScript is a superset of JavaScript. It is a strongly typed language that provides static typing, which helps in catching errors making it ideal for large team collaborations. Being a programming language, TypeScript provides loops to iterate through a collection of items or execute a block of code multiple times. In this Answer, we will explore the implementation of for-loop in TypeScript.

for loop

A for loop is used to iterate through a collection of items or execute a code block for a predefined number of times. The iterable sequence can be a list, string, or a range. The syntax of for loop is given below:

for (initialization ; condition ; increment/decrement){
    // code block
}
For-loop syntax

In the above syntax, we can see that for loop takes:

  • intialization: Here, we initialize an integer loop variable.

  • condition: Here, we define the condition until which the code block should execute.

  • increment/decrement: Here, we increase or decrease the value of the initialized variable.

Example

Let's explore how we can utilize a for loop and execute a code block 10 times:

for(let i = 0 ; i <= 10 ; i++) {
  console.log("Iteration number: "+ String(i+1));
}

The code explanation is given below:

  • Line 1: We initialize the loop variable i with 0 value. The loop will keep executing until the condition i<=10 is true. On each iteration, i++ increases the value of i by 1.

  • Line 2: We print the statement Iteration number: with the current iteration number.

TypeScript provides two distinct types of for-loops that cater to different scenarios:

  • for-in loop

  • for-of loop

for-in loop

The for-in loop is primarily used to iterate through properties of an object, but we can also use it to iterate through an array or string. Below we give examples of both of the use cases:

Iterating through an object

The example below shows how we can use the for-in loop to iterate through the object properties:

const person = { name: "Bob", age: 20, profession: "Lawyer" , gender: "male" };
for (const key in person) { 
    console.log(key +" : "+ person[key])
}

The code explanation is given below:

  • Line 1: We create an object with information related to a person. The object stores data in a key-value pair format.

  • Line 3: We use the for-in loop to iterate through the person object. The key is the loop variable that stores the key of the object in every iteration.

  • Line 4: We print the key and value (person[key]) of the object.

Iterating through an array

The example below shows how we can use the for-in loop to iterate through an array:

var animals : any = [ "dog" , "cat" , "goat" , "sheep" ] 
for( var idx in animals ) {
   console.log( animals[idx] )  
}

The code explanation is given below:

  • Line 1: We create an array of animal names.

  • Line 3: We use the for-in loop to iterate through the animals object. idx is the loop variable that stores the array index of the current iteration.

  • Line 4: We print the value of the array at index idx.

for-of loop

The for-of loop is used to directly access the items of an array or characters of a string. Below we can see examples of using for-of loop to iterate through an array and a string.

Iterating through an array

The example below shows how we can use the for-of loop to iterate through an array:

var birds:any = ["sparrow" ,  "eagle" ,  "dove" , "crow" , "raven"] 
for(var bird of birds) {
   console.log(bird)  
}

The code explanation is given below:

  • Line 1: We create an array of bird names.

  • Line 3: We use the for-of loop to iterate through the birds object. bird is the loop variable that stores the array item of the current iteration.

  • Line 4: We print the value stores in the variable bird.

Iterating through a string

The example below shows how we can use the for-of loop to iterate through a string:

var word:string = "Hello" 
for(var char of word) {
   console.log(char)  
}

The code explanation is given below:

  • Line 1: We create a string with Hello value.

  • Line 3: We use the for-of loop to iterate through the word string. char is the loop variable that stores a character of the string in each iteration.

  • Line 4: We print the value stores in the variable char.

Conclusion

for loop is an important tool in any programmer's toolkit. It helps in executing a block of code multiple times according to a pre-defined condition.

Learn about do-while loops

Learn about while loops

Free Resources

Copyright ©2026 Educative, Inc. All rights reserved