Automatic vs Explicit type conversion in javascript.

From the first two examples used in the first part of this series. Here is a link if you missed it, you’ll realize that there are basically two methods of type conversion in Javascript.

From the first example, javascript automatically converted the number to a string which is referred to as automatic type conversion.

console.log(typeof(30 + 'years'));//string

From the second example, we had to introduce an inbuilt javascript function (Number()) to try to convert the string into a number which is referred to as explicit type conversion.

1) Number()

console.log(Number(30 + 'years')); //NaN

This function only works for base 10 integers and does not allow trailing characters. The conversion may not have worked since it was an impossible one, but this function does work where allowed. for example, conversion of a boolean to a number;

console.log(Number(true)); //1
console.log(Number(false)); //0

Here’s is a table that summarizes how primitive type values convert from one type to another in javascript. If you need to learn the difference between primitive and reference types in javascript then have a look at this article.

Other explicit type conversion functions in javascript include;

2) String() / toString()

• String() method attempts to convert the type into a string. Examples;

console.log(typeof(true)); //boolean
console.log(typeof(String(true))); //string

console.log(typeof(1)); //number
console.log(typeof(String(1))); //string

console.log(typeof(true)); //boolean
console.log(typeof(true.toString())); //string

• When using the toString() method the conversion is always in base 10, but if we specify the argument, we can convert into other bases between 2 and 36. Examples;

let age = 100;
console.log(age.toString(2)); //1100100
console.log(age.toString(8)); //144
console.log(age.toString(16)); //64

Apart from null and undefined, all the other types can use the toString() method.

• Javascript does not allow the use of the toString() method on null and undefined types;

let number = null;
number.toString();
console.log(number); //Cannot read property 'toString' of null

let text;
text.toString();
console.log(number); //Cannot read property 'toString' of undefined

3) Boolean()

• Boolean() method attempts to convert the type into boolean. Examples;

console.log(typeof(1)); //number
console.log(typeof(Boolean(1))); //true - boolean
console.log(typeof(0)); //number
console.log(typeof(Boolean(0))); //false - boolean
console.log(Boolean('hello')); //true - boolean
console.log(Boolean('')); //false- boolean

This marks the end of the second part of a series of blog posts related to type conversion in javascript. If you haven't read the first part click this link to get access.

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