JavaScript Hoisting refers to the process whereby the interpreter appears to move the declaration of functions, variables or classes to the top of their scope, prior to execution of the code.
Hoisting allows functions to be safely used in code before they are declared.
Variable and class declarations are also hoisted, so they too can be referenced before they are declared. Note that doing so can lead to unexpected errors, and is not generally recommended.
The nullish coalescing operator (??) is a logical operator that returns its right-hand side operand when its left-hand side operand is null or undefined, and otherwise returns its left-hand side operand.
The optional chaining operator (?.) enables you to read the value of a property located deep within a chain of connected objects without having to check that each reference in the chain is valid.
The ?. operator is like the . chaining operator, except that instead of causing an error if a reference is nullish (null or undefined), the expression short-circuits with a return value of undefined. When used with function calls, it returns undefined if the given function does not exist.
Show demo below
const arr = ['a', 'b', 'c'];
for (index in arr) { console.log(index); }
//ouput:
//1
//2
//3
Once there lived a hind in a forest. She had a son who had grown very young and strong.
She was very happy to see his stout body and branched strong horns and thought, "stags have powerful horns, why should they be afraid of hounds, wolves then?
It's sheer cowardice. I would never like my son to do it at all. "After some time, the hind's son came there. The hind wanted to teach him to be courageous.
Once a huge oak tree stood on the bank of a river. It was well nourished by the water of the river. Naturally, it was very strong and had a thick stem.
Just nearby, grew some reeds with thin but flexible stems. They stood almost half in water and had flourished well too.One day, strong winds blew.
The tree, though huge and strong, broke from the middle and was thrown across the stream just among the reeds.
It was high summer. A traveller hired a donkey and set out on a journey. The owner of the donkey was following behind to drive the beast. At mid-day, they decided to take rest for some time but couldn't find any shady place around. So, the traveler decided to rest in the shade of the donkey.
Dr Edze Westra, from the University of Exeter, says gene editing techniques such as CRISPR/Cas9 may usher in a golden era of health.
Dr Westra believes the ability to splice selected DNA into cells with great precision is destined to become 'super important' in the next two decades.
He foresees it transforming the human race by creating generations of people for whom cancer, failing vision, and the diseases of old age or bad genes are distant memories.
Dick was seven years old, and his sister, Catherine, was five. One day their mother took them to their aunt’s house to play while she went to the big city to buy some new clothes.
The children played for an hour, and then at half past four their aunt took Dick into the kitchen. She gave him a nice cake and a knife and said to him,
“ Now here’s a knife, Dick. Cut this cake in half and give one of the pieces to your sister, but remember to do it like a gentleman,”
“Like a gentleman?” Dick asked. “How do gentleman do it?”
Building a pandemic-free future won't be easy, but Bill Gates believes that we have the tools and strategies to make it possible -- now we just have to fund them. In this forward-looking talk, he proposes a multi-specialty Global Epidemic Response and Mobilization (GERM) team that would detect potential outbreaks and stop them from becoming pandemics. By investing in disease monitoring, research and development as well as improved health systems, Gates believes we can "create a wo...