Declaration & Expression

Question 1

What is Function Declaration ?

Answer 1

Function that can be used before it’s declared

Example :-

function calAge(birthyear) {
    return 2050 - birthyear;
}

const age1 = calAge(1984)
console.log(age1);

Question 2

What is a Expression ?

Answer 2

Essentially a function value stored in a variable

Example :-

const calAge2 = function (birthyear) {
    return 2037 - birthyear
}

const age2 = calAge2(1991);

console.log( age2)

Question 3

Coding Challenge -
1. The world population is 7900 million people. Create a function declaration called ‘percentageOfWorld1’ which receives a ‘population’ value, and returns the percentage of the world population that the given population
represents.
For example, China has 1441 million people, so it’s about 18.2% of the world population
2. To calculate the percentage, divide the given ‘population’ value by 7900 and then multiply by 100

3. Call ‘percentageOfWorld1’ for 3 populations of countries of your choice, store the results into variables, and log them to the console.
4. Create a function expression which does the exact same thing, called ‘percentageOfWorld2’, and also call it with 3 country populations (can be the same populations)

Answer 3

function percentageOfWorld1(population) {
return (population / 7900) * 100;
}
const percentageOfWorld2 = function (population) {
return (population / 7900) * 100;
};
const percPortugal1 = percentageOfWorld1(10);
const percChina1 = percentageOfWorld1(1441);
const percUSA1 = percentageOfWorld1(332);
console.log(percPortugal1, percChina1, percUSA1);

OUTPUT :-
0.12658227848101267 18.240506329113924 4.2025316455696204