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Let's start with a story to illustrate the concept of type conversion and coercion. Imagine you're a chef trying to make a recipe for a delicious chocolate cake. You have all the ingredients listed in your recipe, but they come in different units of measurement. For example, the recipe calls for 1 cup of sugar, but you only have a bag of sugar that's measured in grams.
You could convert the grams to cups by using a conversion factor, such as 1 cup equals 200 grams of sugar. This is an explicit type conversion, where you're converting the unit of measurement of the sugar from grams to cups.
However, what if the recipe calls for 1 cup of sugar and 1 cup of flour? You have a bag of sugar that's measured in grams and a bag of flour that's measured in ounces. How do you compare the two ingredients?
Type conversion is a deliberate choice made by the developer to convert one data type to another. It can be useful when working with APIs or libraries that require a specific data type. For example, some APIs may require data to be sent in JSON format. In this case, we may need to convert our data to a string before sending it.
Example: Converting a String to a Number
const str = "42"; const num = Number(str); console.log(num + 1); // Output: 43
In this example, the Number() function is used to convert the string "42" to the number 42, which can then be added to 1 to get the result of 43.
Example: Converting a Number to a String
Suppose we have a variable named num that holds the number 42. We can explicitly convert this number to a string by using the toString() method, like so:
let num = 42; let str = num.toString();
In this example, we are converting the num variable from a number to a string using the toString() method. This is an example of type conversion because we are explicitly converting the data type.
Example: Coercing a Number to a String
let num = 42; let str = "The answer is " + num;
let num = 42; let str = "42"; console.log(num == str); // true
Example: Coercing a String to a Boolean
const str = "hello"; const bool = Boolean(str); console.log(bool); // Output: true
In this example, the Boolean() function is used to coerce the string "hello" to the Boolean value true, since it's not an empty string.