Javascript 10 Question ✌✌
- What is the meaning of Null data type?
Null is nothing, the data type of null is an object. A variable with an unknown value can store Null.
NaN means for ‘Not a Number ’. Like,
2. Falsy value: JavaScript has some values that the JavaScript compiler assumes to be false values.😒- false, 0, null, undefined, Nan, Empty String(“ ”).
3. What is the difference between == and === operators?
‘=’ operator is used for assigning values to a variable.
‘==’ operator is used for comparing two variables, but it ignores the datatype of the variable.
‘===’ operator is used for comparing to variables and also checks datatype and compares two values.
4.Object literal in js: A JavaScript object literal is a comma-separated list of property/ attribute and method in curly braces.
we can use a method into an object and we can call it like rect.draw(). But what if you use the property inside that function? What is this?🤦♂️🤦♂️
5.how to understand the this keyword?
point 1- this will always refer to the object that will be used. point 2-
If the object uses this somewhere else, it will always refer to the window object.
But if we use this inside an object, will the object refer? Yes, Then who will refer to the object that will be used. Follow the example of point 4.
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6.Bind, call, Apply: When a function is called, the this keyword always refers to the window object. But what if we want to use the object we created?
There are 3 methods for this. Call, Bind, Apply….
7.What is Synchronous programming?
Synchronous means that you can only execute one thing at a time. (existing and occurring at the same time)-line by line execution.
8.What is Asynchronous Programming?
Asynchronous means that you can only execute multiple things at a time and you don’t have to finish executing the current thing in order to move on to the next one. (not existing and occurring at the same time)
9.What Does V8 engine do?
- Compile and Executes js code
- Handling call stack
- Handling Heap Memory for variables
- Provide Data types, Operators, Objects, and Functions.
10. What is DOM?
It just an API to interact with HTML Document and change it later on-demand. With the HTML DOM, js can access and change all the elements of on HTML document. when a web page is loaded, the browser creates a DOM of the pages. The HTML DOM model is constructed as a tree of objects.
