Using Number.toString() in TypeScript

Using Number.toString() in TypeScript #

Use the Number.toString() method to convert a number to a string in TypeScript, e.g. const str = num.toString(). The Number.toString() method returns a string that represents the specified number. When used on negative numbers, the sign is preserved after the conversion.

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const num = 701;

// ✅ Use Number.toString()
const str = num.toString();
console.log(str); // 👉️ "701"
console.log(typeof str); // 👉️ "string"

// ✅ Alternatively, use String()
const strAgain = String(num);
console.log(strAgain); // 👉️ "701"
console.log(typeof strAgain); // 👉️ "string"

We used the Number.toString method to convert a number to a string in TypeScript.

The method returns a string that represents the given number.

If you call the Number.toString() method on a negative number, the sign is preserved.

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const num = -51;

const str = num.toString();
console.log(str); // 👉️ "-51"

If the Number.toString() method is called on a number with a decimal, the decimal is preserved.

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const num = 14.54;

const str = num.toString();
console.log(str); // 👉️ "14.54"
console.log(typeof str); // 👉️ "string"

The dot sign in the string is used to separate the decimal places.

Note that you can't directly call the Number.toString() method on a number.

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// ⛔️ Error: An identifier or keyword cannot
// immediately follow a numeric literal.ts(1351)
const str = 7.toString();

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

To get around this, we have to wrap the number literal in parenthesis before calling the toString() method.

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const str = (7).toString();

Perhaps a better approach in this situation is to use the String() function.

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const str = String(7);
console.log(str); // 👉️ "7"
console.log(typeof str); // 👉️ "string"

The String function also converts a number to a string, but solves this issue seamlessly, because we aren't calling any built-in methods on the number literal.

It also preserves the negative sign and the decimal part when converting numbers to strings.

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const str = String(-7);
console.log(str); // 👉️ "-7"

const str2 = String(7.432);
console.log(str2); // 👉️ 7.432

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.