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Which is the the best way (if there is one) to cast from number to string in Typescript?

var page_number:number = 3;
window.location.hash = page_number; 

In this case the compiler throws the error:

Type 'number' is not assignable to type 'string'

Because location.hash is a string.

window.location.hash = ""+page_number; //casting using "" literal
window.location.hash = String(number); //casting creating using the String() function

So which method is better?

Which is the the best way (if there is one) to cast from number to string in Typescript?

var page_number:number = 3;
window.location.hash = page_number; 

In this case the compiler throws the error:

Type 'number' is not assignable to type 'string'

Because location.hash is a string.

window.location.hash = ""+page_number; //casting using "" literal
window.location.hash = String(number); //casting creating using the String() function

So which method is better?

• javascript
• casting
• typescript

Share Improve this question Follow edited Sep 13, 2015 at 21:46 Jeroen 63.5k4646 gold badges227227 silver badges365365 bronze badges asked Sep 13, 2015 at 21:15 Ma JerezMa Jerez 5,97544 gold badges2525 silver badges2222 bronze badges

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8 Answers 8

Sorted by: Reset to default 460

"Casting" is different than conversion. In this case, window.location.hash will auto-convert a number to a string. But to avoid a TypeScript compile error, you can do the string conversion yourself:

window.location.hash = ""+page_number; 
window.location.hash = String(page_number); 

These conversions are ideal if you don't want an error to be thrown when page_number is null or undefined. Whereas page_number.toString() and page_number.toLocaleString() will throw when page_number is null or undefined.

When you only need to cast, not convert, this is how to cast to a string in TypeScript:

window.location.hash = <string>page_number; 
// or 
window.location.hash = page_number as string;

The <string> or as string cast annotations tell the TypeScript compiler to treat page_number as a string at compile time; it doesn't convert at run time.

However, the compiler will complain that you can't assign a number to a string. You would have to first cast to <any>, then to <string>:

window.location.hash = <string><any>page_number;
// or
window.location.hash = page_number as any as string;

So it's easier to just convert, which handles the type at run time and compile time:

window.location.hash = String(page_number); 

(Thanks to @RuslanPolutsygan for catching the string-number casting issue.)

Utilize toString() (or toLocaleString(), but take care that it might add things like 1000's separator characters), for example:

var page_number:number = 3;
window.location.hash = page_number.toString();

---

These throw an error if page_number is null or undefined. If you don't want that you can choose the fix appropriate for your situation:

// Fix 1:
window.location.hash = (page_number || 1).toString();

// Fix 2a:
window.location.hash = !page_number ? "1" page_number.toString();

// Fix 2b (allows page_number to be zero):
window.location.hash = (page_number !== 0 && !page_number) ? "1" page_number.toString();

// Fix 3, modern js:
window.location.hash = page_number?.toString() || "1";

One can also use the following syntax in typescript. Note the backtick " ` "

window.location.hash = `${page_number}`

This is some short ways

any_type = "" + any_type; 
any_type = String(any_type); 
any_type = `${any_type}`;

window.location.hash is a string, so do this:

var page_number: number = 3;
window.location.hash = String(page_number); 

Just use: page_number?.toString()

Easiest way:

var num = 3; var str =`${num}`;

const page_number = 3;

window.location.hash = page_number as string; // Error

"Conversion of type 'number' to type 'string' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first." -> You will get this error if you try to typecast number to string. So, first convert it to unknown and then to string.

window.location.hash = (page_number as unknown) as string; // Correct way

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