Functions(函数)

function logger() {
    console.log('My name is Shubham');
}
// calling / running / invoking function（调用/运行/调用函数 ）
logger();    //My name is Shubham
logger();    //My name is Shubham

function fruitProcessor(apples, oranges) {
    const juice = `Juice with ${apples} apples and ${oranges} oranges.`;
    return juice;
}

const appleJuice = fruitProcessor(5, 0);
console.log(appleJuice);  //Juice with 20 piece of apple and 0 pieces of orange.

const appleOrangeJuice = fruitProcessor(2, 4);
console.log(appleOrangeJuice);  //Juice with 8 piece of apple and 16 pieces of orange.

const num = Number('23');
console.log(num);    //23

Function Declarations vs. Expressions（函数声明 vs 函数表达式）

Function Declarations

function calcAge1(birthYeah) {
    return 2021 - birthYeah;
}
const age1 = calcAge1(1999);
console.log(age1);    //22

Function expression

const calcAge2 = function (birthYeah) {
    return 2021 - birthYeah;
}
const age2 = calcAge2(1999);
console.log(age2);    //22

Arrow functions(箭头函数)

const calcAge3 = birthYeah => 2021 - birthYeah;
const age3 = calcAge3(1999);
console.log(age3);    //22

const yearsUntilRetirement = (birthYeah, firstName) => {
    const age = 2021 - birthYeah;
    const retirement = 60 - age;
    // return retirement;
    return `${firstName} retires in ${retirement} years`;
}

console.log(yearsUntilRetirement(1991, 'Jonas'));    //Jonas retires in 30 years
console.log(yearsUntilRetirement(1980, 'Bob'));    //Bob retires in 19 years

Functions Calling Other Functions(调用其他函数的函数)

function cutFruitPieces(fruit) {
    return fruit * 4;
}

function fruitProcessor(apples, oranges) {
    const applePieces = cutFruitPieces(apples);
    const orangePieces = cutFruitPieces(oranges);

    const juice = `Juice with ${applePieces} piece of apple and ${orangePieces} pieces of orange.`;
    return juice;
}
console.log(fruitProcessor(2, 3));    //Juice with 8 piece of apple and 12 pieces of orange.