How to Convert a String to Number in Typescript?

The Typescript way to do this would be:

Number('1234') // 1234
Number('9BX9') // NaN

as answered here:

For our fellow Angular users:

Within a template, Number(x) and parseInt(x) throws an error, and +x has no effect. Valid casting will be x*1 or x/1.

As shown by other answers here, there are multiple ways to do the conversion:

Number('123');
+'123';
parseInt('123');
parseFloat('123.45')

I'd like to mention one more thing on parseInt though.

When using parseInt, it makes sense to always pass the radix parameter. For decimal conversion, that is 10. This is the default value for the parameter, which is why it can be omitted. For binary, it's a 2 and 16 for hexadecimal. Actually, any radix between and including 2 and 36 works.

parseInt('123')         // 123 (don't do this)
parseInt('123', 10)     // 123 (much better)

parseInt('1101', 2)     // 13
parseInt('0xfae3', 16)  // 64227

In some JS implementations, parseInt parses leading zeros as octal:

Although discouraged by ECMAScript 3 and forbidden by ECMAScript 5, many implementations interpret a numeric string beginning with a leading 0 as octal. The following may have an octal result, or it may have a decimal result. Always specify a radix to avoid this unreliable behavior.

— MDN

The fact that code gets clearer is a nice side effect of specifying the radix parameter.

Since parseFloat only parses numeric expressions in radix 10, there's no need for a radix parameter here.

More on this:

• Why do we need to use radix? (SO Question)
• SO Answer to "What is the difference between parseInt() and Number()?"

Expounding on what Ryan said, TypeScript embraces the JavaScript idioms in general.

var n = +"1"; // the unary + converts to number
var b = !!"2"; // the !! converts truthy to true, and falsy to false
var s = ""+3; // the ""+ converts to string via toString()

All the interesting in-depth details at JavaScript Type Conversion.

String to number conversion:

In Typescript we convert a string to a number in the following ways:

• parseInt(): This function takes 2 arguments, the first is a string to parse. The second is the radix (the base in mathematical numeral systems, e.g. 10 for decimal and 2 for binary). It then returns the integer number, if the first character cannot be converted into a number, NaN will be returned.
• parseFloat(): Takes as an argument the value which we want to parse, and returns a floating point number. If the value cannot be converted to a number, NaN is returned.
• + operator: The operator when used appropriately can coerce a string value into a number.