#8 Type Conversion & Coercion in JavaScript
Summary
TLDRIn this JavaScript tutorial by Davin Rady, the concept of type conversion and type coercion is explored. The video explains how data types like numbers, strings, and booleans can be explicitly converted using language-specific functions. It also delves into implicit type coercion, where JavaScript automatically changes data types during operations, leading to potential bugs if not carefully managed. The tutorial covers practical examples, such as converting numbers to strings for storing zip codes and telephone numbers, and discusses the importance of being vigilant with these operations to avoid unexpected results.
Takeaways
- 😀 The video discusses type conversion and type coercion in JavaScript, explaining the difference between the two concepts.
- 🔢 Data types in JavaScript include numbers, strings, booleans, and the need to convert data between these types for various operations.
- 💡 Type conversion is explicit, where developers use specific functions like `String()` or `Number()` to change data types.
- 📝 Type coercion is implicit, where JavaScript automatically changes data types to perform operations, such as when adding a number and a string.
- 👀 The `typeof` operator is used to check the data type of a variable in JavaScript.
- 📌 Storing data like zip codes or phone numbers as strings is recommended when no calculations are needed.
- 🔄 The plus (`+`) operator can perform both addition and string concatenation, depending on the types of operands involved.
- 🤔 JavaScript's type coercion can sometimes lead to unexpected results and bugs if not handled carefully.
- 👍 JavaScript is appreciated for its flexibility in understanding the developer's intent and performing type coercion to meet that intent.
- 🚫 However, JavaScript's automatic type coercion can also be frustrating when it overrides the developer's intended operations.
- 🔍 The video suggests using functions like `parseInt()` to convert strings to integers, especially when the string contains non-numeric characters at the start.
Q & A
What is the main topic of the video?
-The main topic of the video is JavaScript type conversion and type coercion.
Why is type conversion necessary in programming?
-Type conversion is necessary when you want to change the data format, for example, converting a number to a string or vice versa, to meet specific requirements such as storing a zip code as a string.
What is the purpose of the 'typeof' operator in JavaScript?
-The 'typeof' operator is used to print the type of data of a variable in JavaScript.
How can you convert a number to a string in JavaScript?
-You can convert a number to a string in JavaScript by using the String function and passing the number as an argument, like String(num).
What happens when you try to perform an operation with a number and a string using the plus (+) operator?
-When using the plus (+) operator with a number and a string, JavaScript performs type coercion and treats the operation as string concatenation, converting the number to a string.
How does JavaScript handle type coercion with the subtraction operator?
-With the subtraction operator, JavaScript converts the string to a number if possible, allowing the operation to proceed as a numerical subtraction.
What is the result of converting a non-zero number to a boolean in JavaScript?
-In JavaScript, converting a non-zero number to a boolean results in true, as all non-zero numbers are considered truthy values.
What is the result of converting zero to a boolean in JavaScript?
-In JavaScript, converting zero to a boolean results in false, as zero is considered a falsy value.
How can you convert a string that represents a number into an actual number in JavaScript?
-You can use the parseInt function to convert a string that represents a number into an actual number in JavaScript.
What does the unary plus (+) operator do when used with a string in JavaScript?
-The unary plus (+) operator attempts to convert the string into a number in JavaScript.
What are some of the falsy values in JavaScript?
-In JavaScript, falsy values include 0, null, undefined, NaN, '', and false.
What is the difference between type conversion and type coercion in JavaScript?
-Type conversion is the explicit action of a developer to convert data from one type to another using functions like String(), Number(), or Boolean(). Type coercion is an implicit action performed by JavaScript where the engine changes the type of data during an operation to make it compatible, such as when adding a number and a string.
Outlines
🔢 JavaScript Type Conversion Basics
In this paragraph, Davin Rady introduces the concept of type conversion and coercion in JavaScript. He explains the necessity of converting data types like numbers, strings, and booleans for various programming requirements. Davin demonstrates how to explicitly convert a number to a string using the String() function and vice versa with the Number() function. He also touches on the topic of converting numbers to boolean values, setting the stage for a deeper dive into type coercion and its implications in subsequent paragraphs.
🤔 Understanding Type Coercion in JavaScript
This paragraph delves into the automatic process of type coercion in JavaScript. Davin Rady illustrates how JavaScript handles operations between different data types, such as adding a number and a string, which results in the number being coerced into a string to perform concatenation. He further explains that subtraction between a string and a number will coerce the string into a number. Davin also discusses the behavior of boolean values with the NOT operator and how different values are treated as truthy or falsy in JavaScript, with zero and null being the only falsy values, while all others are truthy.
🛠️ Advanced JavaScript Type Conversion Techniques
The final paragraph focuses on advanced type conversion techniques in JavaScript. Davin Rady discusses the use of unary plus to convert a string to a number and the potential issues that can arise from JavaScript's type coercion, such as unexpected NaN (Not a Number) results. He introduces the parseInt function as a method to extract integer values from strings, highlighting its limitations when encountering non-numeric characters. Davin emphasizes the importance of being cautious with type operations to avoid bugs and encourages viewers to explore various type conversion functions available in JavaScript.
Mindmap
Keywords
💡Type Conversion
💡Type Coercion
💡Data Types
💡Boolean
💡Unary Operators
💡Concatenation
💡Truthy and Falsy Values
💡NaN
💡parseInt
💡Variable Assignment
💡JavaScript
Highlights
Introduction to type conversion and type coercion in JavaScript.
Explanation of why type conversion is necessary, such as converting data from number to string or vice versa.
Demonstration of using the 'typeof' operator to print the data type of a variable.
How to convert a number to a string format using the String() function.
Example of converting a string to a number using the Number() function.
Discussion on the concept of type conversion as explicit conversion by the developer.
Introduction to type coercion as implicit conversion performed by JavaScript.
Illustration of how JavaScript handles the plus operator with different data types, leading to type coercion.
Explanation of how JavaScript converts types based on the operator used, such as converting a string to a number with the subtraction operator.
The impact of using the 'not' operator on boolean values and how it affects type conversion.
Understanding truthy and falsy values in JavaScript, with examples including numbers and null.
The unique behavior of zero as a falsy value when converting numbers to boolean.
How JavaScript handles type coercion with the unary plus operator to convert strings to numbers.
The use of parseInt function to convert strings that represent integers into actual numbers.
The importance of being cautious with type coercion to avoid unexpected bugs in JavaScript.
Encouragement for viewers to explore different type conversion functions and understand their applications.
Conclusion and invitation for feedback on the video content.
Transcripts
[Music]
welcome back aliens my name is davin rady and let's continue with this series on javascript
now in this video we'll talk about type conversion and type coercion now why do we have two different
words let's understand that now first of all it doesn't matter which language you work with
you have something in common right you actually work with data but sometimes you want to convert
your data in specific format example we have talked about data types right we have numbers
string boolean and there might be an option or there might be a requirement where you have
to convert your data from number to string or from string to number or from number to boolean
how do we do that now let's say let me create a variable here so i will say num this time i'm
using a dark theme basically a high contrast so let me know your feedback in the comments section
uh so finally we are on the dark theme yeah let me create a number here right so this is a number
now we have seen how do you print the type of data of course when you want to print the data as it
is we can simply print num right now this will print data example if i run this code you got 6
but what if you want to print a type of it in that case you can use a very special
operator which we have seen earlier which is type off and you can print the type of num
so basically we are printing two things here we are printing num and we are printing type of num
and let's see what happens and you can see we got six and we got number that means the type
of this num is number that is working right but what if i want to store this num in a different
format i want this to be in string format can we do this now you will think hey why do we do that
so example let's say if you want to store a pin called a zip code of area which is the best
format should you store the zip code in number or in a string format see whenever you don't
want to perform any operation it's better to store that in a string format example telephone number
zip code or whatever big number you have when you want to perform calculation that's why
number makes sense right so here i want to store this six in a string format in that case you have
to convert that right you have to perform some operation so we have a specific thing
called a string so we'll pass string here when you pass this number 6 inside a string
it will give you a string format so this number is getting stored in a string format now
will it work let's try so let me just run this code once again and you can see we got six
no change in data of course you have not got s i x what you got is number six and you got a string
okay so this is working right and you can also do reverse if you have a number in a string format
let's say one two three so now if you run this code of course the data is in string format 123
is in string format and if you want to perform operation you have to convert that into number
in order to do that we can simply say number and you can give a bracket and this will work
right so if you run this code you got number the same thing again you can do with boolean okay so
you can convert a number up with boolean but that's a different thing we'll do that later
the interesting thing is this is type conversion right you are able to convert a number
in different format this is explicit conversion because basically you as a developer you are
trying to convert a data from one format to the format it's working right but then javascript
went ahead javascript says hey you have type conversions that's great let me give you something
called type conversion now what it means so let's say i have a number here i'll say num or maybe
i will not go for any specific name because num represents a name right so i will go with
let's say x i know it's not a good variable name but just for the example here we can go with it
so let's say i have a variable x and i want to print x here and i want to print the type
of it of course we are printing the data we are printing the type of this data and the output
you are getting is undefined undefined of course that makes sense right now what i will do here is
i will assign data to it so when you assign the data it will change the type of it now what did i
want to assign let me just do that here so i will say x is equal to six or maybe a different number
this time so let's go for x equal to eight now if we do the same thing i just want to copy and paste
actually where i'm just reusing the code right so after changing the value of x now let's try so
you can see we got undefined undefined because that was the first time and then we got eight
number because this is the number if i change the same thing again let's say i want to perform
some operation so i can simply say x is equal to i want to add x with a string what do you think what
would happen and what type of string i want to add maybe i just want to add empty string i don't
even have some specific type of string here right it's it's an empty string now what will happen of
course i should also print the console here okay now let me try and you can see this time we got
string so basically whenever you have a number and you are you have a string this plus operator here
it got confused the idea behind a plus operator is to add two numbers right but this time we have a
number and a string confusion right so coercion comes into picture so javascript says okay in
this case every time you have two different data and you want to perform some operation you have
to come to some consensus right either both has to be same type it either it should be both string or
both number so in this case it goes for the string because we have string at one end now whenever you
have string and when you use plus operator it is actually concatenation so basically we are joining
two strings for example let's say you have naveen you have ready two different strings you use a
plus orbital basically you are concatenating it in this case as well even if you have x which is the
number and you have a string it will convert that into string but not always not always when you use
a string a number it will give the same results example let's say at this point if you see this is
a type of string right this x is a type of string what if i do x equal to x minus 2. now you tell me
what will happen of course i have to print it as well so pause this video and let me know what will
happen because x is a string now 2 is a number so how it should behave should we get 8 minus 2 6 or
should we get some weird answer or maybe it should be nand right which is because you are subtracting
a number from a string and that is weird so let's let's see what happens so if you run this code
i hope you have answered that in the comment section you got number so this is what happens
when you have a subtraction operator with a string it will convert that into number so this is type
coercion so based on what type of operator you're using based on what's the requirement javascript
engine will change that for you in fact we can also do with boolean so we know right boolean is
true or false now the way you can manipulate boolean is with the help of some operators
one of them is exclamation exclamation will simply replace or it will do the opposite so if it is
true it will give you false if it is false it will give you true right so exclamation actually means
not so there's a not operator with boolean which will change the type so from true to false false
true now let me just do that so i will say x equal to not x so even if it is a number format so you
can see x in this case is number right so you are applying a not operator or number because
the naught will only work with boolean right and you are giving a number so in this case it will
convert that into boolean and then it will perform the not operation and let's see what happens but
the question is will you get true or false so even if i say it converts this from number to
boolean what happens is it true or false let's try let's run this code oh i'm not printing it my bad
let me print this and you can see we got false boolean so boolean makes sense but why false
that means you are performing an operation the output of that operation is false that means
initially the value of x was true that means if you try to convert a number into boolean
if that number is 6 it will give you true only 6 it's actually any number example let me just
do that so what i will do is i will just go to console and console.log and let me convert
a number let's say i have a number seven and i want to convert this into boolean how do we
convert a number into boolean the same way we did it for the number and string with the help of that
keyword number string here let me use boolean so i'm passing 7 to a boolean right so it will
convert this 7 into a boolean format but what you will get you will you get true or false let's try
so when i run this code you can see we got true okay so for six it just giving you true for seven
is giving you true i thought it will be even odd so even numbers will get true or number will get
false but that's not the case every number is giving you true let me try negative number
so if i say minus seven let's see it's still true okay now after trying out all
the different combinations let's try zero and the moment you try zero and if you underscore
you can see we got false that means all the numbers are true only zero is false
why is because the actual implementation of boolean happens in that way 0 is false 1 is
true right if it is not 0 everything is true but you can actually calculate with each number so
they simply go with simple formula if it is 0 it's false if it is all the other numbers it is true
and this is called uh truthy and the falsie values i know that that's tricky it's not just with
numbers it's also with other types example let me convert into boolean of type null now what will
happen if we try to convert null into boolean and if you're on this code you can see we got false so
even null is a false value so whenever you try to convert something into boolean and if that gives
you false it is false value if you pass something and if you're trying to convert that into boolean
if it is giving you true that's called a truthy value example after some time will start working
with functions objects whatever your data you pass so if you try to convert object into boolean it
will give you true if you try to pass a function to and convert into boolean it will give you true
cool what about undefined let me just try that so we'll try it with undefined also it will give
you false so these are all false values okay apart from this everything is truthy value so
you can see the list if you have something like this and if you try to convert these things into
boolean you will get false and all the other thing will give you true uh let me just try
with stringer we have not tried with string yet so what i will do is i'll pass the string like naveen
now what happens nobody is true or false of course nothing is true let's try and you can see we got
true now since it's not a part of the false values it's true so just reiterate whenever you have a
number and a string it will convert that into string when you apply the addition operator but
when you perform this subtraction operator it will convergent number so javascript is smart enough to
know what should be done and that's one thing i love and hate about javascript we love this thing
because it helps you it actually understands what you need and it will give the output the reason i
also hate it is because it tries to convert things the way it wants sometimes you don't intend to do
that and you want others but javascript says okay you're doing this i will allow you and i
will help you here we don't want your help we want others because this will eventually lead to bugs
okay and that's why you have to very alert when you're doing these operations in fact we have
some more ways example let's say i want to do plus operator here right so we have x in string format
here and you want to okay let me just remove this part just to make it simple yeah so we have
x which is string format right so if you run this code so you can see we got 82 because you have
eight here which is x and then you got two so you got 82. but in this case i want to convert this
into a number in that case you can use unary operators of course we'll talk about orbitals
later in detail but so whenever you add a plus here it tries to convert this string into number
let's try that and you can see we got numbers so we got 10 which is the addition of eight and two
and you've got a number okay there are more ways actually to convert the string into integer or
the other format so let me just try that so let's say we have x and the value of x is one two three
navin okay now in this case i want to convert this into a number format but of course you can't
convert that into number format right because we have naveen there so if you try to do that with
the help of a number function so let's say if i do let me just print that first as it is let's
see what happens if you print this and you can see we got one two three naveen okay that works but
if you try to convert that into number because we did that before let's see what happens so if we
try to do that and if you run this code you can see we got nan which is not number we don't want
this what we want is it should be able to convert that and at least fetch these first integer values
so in this case you can actually use parseint so pass int is a special function which will
accept a string it will try to convert that number okay it will do its hard work to convert a string
into number and you can see we got 123 but what happens if you have a character at the start in
this case it will not work so i have to make sure that you have numbers at the start so it will try
to convert that into numbers right so that's how you can do it uh so try out different functions
you can go to google and search for different type conversions functions and you will get those so i
hope you enjoyed this video let me in the comments section and do some stuff for the videos bye you
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