Convert a Number to a String in TypeScript

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.

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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.

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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.

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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.

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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.

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// ⛔️ 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.

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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.

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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.