TypeScript: Convert a bool to string value

Question

I am unable to convert a boolean to a string value in TypeScript.

I have been roaming through documentation and I could not find anything helpful. I have tried to use the toString() method but it does not seem to be implemented on bool.

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Edit: I have almost no JavaScript knowledge and came to TypeScript with a C#/Java background.

Carine

That's odd, the native JS Boolean supports toString. – Bronk

It seems that TypeScript definitely misses this basic implementation. – Carine

Answer 1

This is either a bug in TypeScript or a concious design decision, but you can work around it using:

var myBool: bool = true;
var myString: string = String(myBool);
alert(myString);

In JavaScript booleans override the toString method, which is available on any Object (pretty much everything in JavaScript inherits from Object), so...

var myString: string = myBool.toString();

... should probably be valid.

There is also another work around for this, but I personally find it a bit nasty:

var myBool: bool = true;
var myString: string = <string><any> myBool;
alert(myString);

Spandau

This is an acknowledged bug in TypeScript and is apparently planned to be fixed in the next release (0.8.2) - typescript.codeplex.com/workitem/362 – Serf

toString() will definitely work fine as of 2016 (versions 1.6) – Heartburning

flag: boolean = Boolean("true"); if you need to convert to boolean from string – Dam

Apparently even for TS Version 2.9.0-dev.20180327 toString() will definitely NOT work! Had to use @Fenton's example here for it to work. WEIRD but fact. – Philippeville

Answer 2

For those looking for an alternative, another way to go about this is to use a template literal like the following:

const booleanVal = true;
const stringBoolean = `${booleanVal}`;

The real strength in this comes if you don't know for sure that you are getting a boolean value. Although in this question we know it is a boolean, thats not always the case, even in TypeScript(if not fully taken advantage of).

Serf

Answer 3

One approach is to use the Ternary operator:

myString = myBool? "true":"false";

Warr

One advantage of this approach is the converted string becomes literal types of "true" | "false" – Piapiacenza

Answer 4

return Boolean(b) ? 'true':'false'

Invade

While this code may answer the question, providing additional context regarding how and/or why it solves the problem would improve the answer's long-term value. You can find more information on how to write good answers in the help center: stackoverflow.com/help/how-to-answer . Good luck 🙂 – Keefer

If b is already a boolean, why use Boolean(b)? – Earflap

Answer 5

This if you have to handle null values too:

stringVar = boolVar===null? "null" : (boolVar?"true":"false");

Cherie

Answer 6

if you know your value is always true/false, you can use JSON.stringify(myBool) it will give you value like 'true' or 'false'

Bionics

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