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How To Convert A String To A Number In TypeScript?

Tim Mouskhelichvili
Tim Mouskhelichvili
2 minutes to read

When coding with TypeScript, developers sometimes need to convert a string to a number. Luckily, JavaScript provides many different ways to do it that you can also use in TypeScript.

The easiest way to cast a string to a number in TypeScript is to use the Number constructor like so:

typescriptconst myString = '444222';
const myNumber = Number(myString);

// Outputs: 444222
console.log(myNumber);

This article will go through different methods of converting a string to a number in TypeScript and show how to use each.

Let's get to it 😎.

How To Convert A String To A Number In TypeScript?

Method #1 - Using the Number constructor

Perhaps, the easiest way to cast a string to a number is to use the JavaScript Number constructor.

This function works with integers and with floats.

typescript// Outputs: 9999
console.log(Number('9999'));

// Outputs: NaN
console.log(Number('asdqwewe2'));

Note: If the function cannot cast the string into a number, it will return a NaN (not a number).

Method #2 - Using the parseInt function

The JavaScript parseInt function only works with integers.

If you attempt to pass a string with floating-point values, they will be cut off.

typescript// Outputs: 55
console.log(parseInt('55'));

// Outputs: 23
console.log(parseInt('23.22'));

Method #3 - Using the parseFloat function

The parseFloat function behaves the same as the parseInt function, except it accepts floating point values.

typescript// Outputs: 55
console.log(parseFloat('55'));

// Outputs: 23.22
console.log(parseFloat('23.22'));

Method #4 - Using multiplication by one

One less known JavaScript trick is to multiple a string by one, which converts the string into a number.

Here is how to do in TypeScript:

typescript// Outputs: 2323.12
console.log("2323.12" as any * 1);

// Outputs: 444
console.log("444" as any * 1);

// Outputs: -55
console.log("-55" as any * 1);

As you can see, you must first cast the string to an any type.

Otherwise, the TypeScript compiler will complain.

Method #5 - Using the double tilde operator

Using the double tilde operator, you can convert a string to a number in TypeScript.

However, values after the decimal point will be cut off.

typescript// Outputs: 2323
console.log(~~"2323.12");

// Outputs: 444
console.log(~~"444");

Final thoughts

As you can see, you have plenty of methods to choose from when casting a string to a number.

When it comes to me, most of the time, I use the Number constructor.

typescript convert string to number

Here are some other TypeScript tutorials for you to enjoy:

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