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What is JavaScript(JS)?
- JavaScript is a lightweight, interpreted programming language with object-oriented capabilities that allows you to build interactivity into otherwise static HTML pages.
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What are the features of JavaScript?
- JavaScript is a lightweight, interpreted programming language.
- JavaScript is designed for creating network-centric applications.
- JavaScript is complementary to and integrated with Java.
- JavaScript is complementary to and integrated with HTML.
- JavaScript is open and cross-platform.
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What are the advantages of JavaScript?
- Less server interaction? You can validate user input before sending the page off to the server.
- Immediate feedback to the visitors? They don’t have to wait for a page reload to see if they have forgotten to enter something.
- Increased interactivity? You can create interfaces that react when the user hovers over them with a mouse or activates them via the keyboard
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Why is javascript called Richer Interface?
- You can use JavaScript to include such items as drag-and-drop components and sliders to give a Rich Interface to your site visitors.
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Is javascript case-sensitive?
- Yes, JavaScript is a case-sensitive language. This means that language keywords, variables, function names, and any other identifiers must always be typed with a consistent capitalization of letters.
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How can we create an object in JS?
var object = { name: "obj", age: 10 };
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How can we read the properties of an object in js?
- Can write and read properties of an object using the dot(.) notation.
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How to create an array in js and how to read array elements?
Can you define arrays using the array literal as follows?- var x = [];
- var y = [1, 2, 3, 4, 5];
An array has a length property that is useful for iteration. Can we read elements of an array as follows?
for (var i = 0; i < x.length; i++)
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How many types of functions JS support?
- A function in JavaScript can be either named or anonymous.
- How to define an anonymous function?
- An anonymous function can be defined in a similar way as a normal function but it would not have any name.
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Which built-in method calls a function for each element in the array?
- forEach method calls a function for each element in the array.
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Which type of variable among global and local, takes precedence over other if names are same?
- A local variable takes precedence over a global variable with the same name.
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Difference between “var” and “let” Keywords?
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Var was there from the beginning but the let was introduced in ES2015/ES6.
Let has block scope and “Var” has function scope
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Var was there from the beginning but the let was introduced in ES2015/ES6.
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Difference between “==” and “===” ?
- ” ==” only compares values “===” compare values and type both.
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Difference between “undefine” and “NULL” Keywords?
- When you define a var but not assign any value. typeof(undefine)=> undefine
Null- manually done. typeof(null)=> object
- When you define a var but not assign any value. typeof(undefine)=> undefine
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What is prototypal Inheritance?
- Every object has a property called a prototype, where we can add methods to it and when you create another object from these the newly created object will automatically inherit its parent’s property.
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Which built-in method sorts the elements of an array?
- Sort method sorts the elements of an array.
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Which built-in method reverses the order of the elements of an array?
- Reverse method reverses the order of the elements of an array ?? the first becomes the last, and the last becomes the first.
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What is SetTimeout()?
- When you setTimeout it becomes asynchronous and it has to wait on the stack to get everything got finished
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How to add one new element at end of an array in javascript?
- Push method adds one or more elements to the end of an array and returns the new length of the array.
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What is closure and how do you use it?
- When a function returns the other function the returning function will hold its environment and this is known as closure.
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Output of below statements
<script>
document.write({});
</script>
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How can you move element in lowercase to uppercase from an array?
- toUpperCase method returns the calling string value converted to upper case.