Boolean type conversion in JavaScript

Now we will look at how the special values true and false behave when converted to strings or numbers. You will need this knowledge in the following lessons.

So, let's try to convert to a string using the function String:

alert(String(true)); // shows 'true' alert(String(false)); // shows 'false'

As you can see, the value true is converted to the string 'true', and the value false is converted to the string 'false'. That is, when you try to add a string and a boolean value, this boolean value will be converted to a string and the strings will be concatenated:

alert('a' + true); // shows 'atrue'

When cast to a number, the value true is converted to the number 1, and the value false is converted to the number 0:

alert(Number(true)); // shows 1 alert(Number(false)); // shows 0

Boolean values are first converted to a number in all mathematical operations. An example:

alert(true + 1); // shows 2 alert(true + true); // shows 2

Without running the code, determine what will be displayed on the screen:

alert(true + 3);

Without running the code, determine what will be displayed on the screen:

alert(true + true);

Without running the code, determine what will be displayed on the screen:

alert(true - true);

Without running the code, determine what will be displayed on the screen:

alert(true + false);

Without running the code, determine what will be displayed on the screen:

alert('1' + true);

Without running the code, determine what will be displayed on the screen:

alert( String(true) + 1 );

Without running the code, determine what will be displayed on the screen:

alert( String(true) + Number(true) );
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