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Script tag You can insert JavaScript program into HTML document using the <script> tags. You can write inline scripts directly between the tags or you can include external scripts. In order to include external script you would specify the src attribute for t...

Variables A named storage for storing data. There are couple way of creating a variable var keyword This is the relic of the past, back when JavaScript first came out it was the only way of declaring variables with the var keyword. Variable declared with ...

String Conversion You can call the String() function to explicit convert a value to a string String(false) -> "false" String(null) -> "null" Numeric Conversion Occurs when you use math functions and expressions console.log("6" / "2"); // Print out 3! Or...

Math Operators +, addition -, subtraction *, multiplication /, division %, remainder **, exponentiation String Operators The plus symbol if used with Strings will be for concatenation, you join two String together. If any of the operand is a String, th...

Ternary Operator let accessAllowed; if (age > 18) { accessedAllowed = true; } else { accessedAllowed = false; } // Can be simplified into just accessedAllowed = age > 18 ? true : false; || (OR) Returns true if one of the boolean value is tru...

While and for loop They are the same as in Python, C, and Java while (condition) { // Repeat certain code } for (begin; condition; step) { // Repeat certain code } break and continue both works the same way as in any other language. Switch state...

Function Declaration To declare a function follow the syntax: function function_name(parameter1, parameter2, ..., parameterN) { // Body of the function } The function can have access to outer variable, as well as modifying it. The outer variable is only...

Objects In JavaScript objects are used to store key to value pair collection of data. You can think of them as dictionary in Python. You can create an object using brackets { }, and a list of optional properties that the object will have. For example: let e...

Reachability In JavaScript garbage collection is implemented through something called reachability. Variable that are reachable are kept in memory and not deleted by the garbage collector. A value is considered to be reachable if it's reachable from a root ...

Constructor function Function that is meant to be a constructor are named with capital letter first and be executed with the new operator. We use a constructor because it creates a shorter and simpler syntax compared to creating object with {...} every time....

Optional chaining There is this problem that if the object that you are accessing might or might not contain an object attribute say address and you can trying to access address's attribute further say user.address.street, then your JavaScript will crash beca...