Convert a Number to a String in TypeScript

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Borislav Hadzhiev

Tue Mar 08 20222 min read

Convert a Number to a String in TypeScript #

Use the String() object to convert a number to a string in TypeScript, e.g. const str = String(num). When used as a function, the String object converts the passed in value to a primitive string and returns the result.

index.ts
const num = 100; // ✅ Convert Number to String // 👇️ const str: string const str = String(num); console.log(str); // 👉️ "100" console.log(typeof str); // 👉️ "string" // ✅ Convert String to Number const backToNumber = Number(str); console.log(backToNumber); // 👉️ 100

We used the String function to convert a number to a string in TypeScript.

The only parameter the function takes is the value that will be converted to a string.

If you convert a negative number to a string, the sign is preserved.

index.ts
const num = -100; const str = String(num); console.log(str); // 👉️ "-100" console.log(typeof str); // 👉️ "string"

If you pass a number with a decimal to the String() function, the decimal is preserved.

index.ts
const num = 14.5; const str = String(num); console.log(str); // 👉️ "14.5"

You might also see the Number.toString method used to achieve the same result.

index.ts
const num = 100; const str = num.toString(); console.log(str); // 👉️ "100" console.log(typeof str); // 👉️ "string"

The Number.toString() method also converts a number to a string.

However, note that you can't directly call a method on a number.

index.ts
// ⛔️ Error: An identifier or keyword // cannot immediately follow a numeric literal. const str = 100.toString();

The example shows how trying to call a built-in method on a number throws an error.

If you are in that situation, wrap the number in parenthesis before calling the built-in method.

index.ts
const str = (100).toString(); console.log(str); // 👉️ "100" console.log(typeof str); // 👉️ "string"

When using the Number.toString() method, the sign is also preserved after the conversion.

index.ts
const str = (-100).toString(); console.log(str); // 👉️ "-100" console.log(typeof str); // 👉️ "string"

Which approach you pick is a matter of personal preference. I prefer using the String() function as I it more widely used in the codebases I've worked on.

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