Javascript Array – 月与灯依旧

Handle element in an Array

const hobbies = ["sports", "cooking", "reading"];

console.log(hobbies[0]);       # Get single element

hobbies.push("surfing");       # Add new element to the end
hobbies.unshift("movies");     # Add new element to th start

hobbies.pop();                 # remove the last element
hobbies.shift();               # remove the first element

Find element

const index = hobbies.findIndex((item) => {
    return item === "reading"
});
console.log(index);

A shorter code:

const index = hobbies.findIndex((item) => item === "reading");
console.log(index);

// Result
2

Find an element in Object

const inventory = [
  { name: "apples", quantity: 2 },
  { name: "bananas", quantity: 0 },
  { name: "cherries", quantity: 5 },
];

const result = inventory.find(({ name,quantity }) => name === "cherries");

console.log(result); 

// Result:
 { name: 'cherries', quantity: 5 }

find() method ONLY returns the first element in the provided array that satisfies the provided testing function

Filter

const words = ['spray', 'elite', 'exuberant', 'destruction', 'present'];
const result = words.filter((word) => word.length > 6);

// Result:
["exuberant", "destruction", "present"]

Iterate Array

const newHobbies = hobbies.map((item) => item + "!");
consoloe.log(newHobbies);

// Result
(3) ["sports!", "cooking!", "reading!"]

Combine Array

const numbers = [1,2,4,5];
const all = [...hobbies, ...numbers];
console.log(all);

// Result
(7) ["sports", "cooking", "reading", 1, 2, 4, 5]

Destruct an Array

const userName = ["John", "Ted"];

// Old School Way
// const firstName = userName[0];
// const lastName = userName[1];

// New Way
const [firstName, lastName] = ["John", "Ted"];
console.log(firstName);
console.log(lastName);

// Result:
John
Ted

We can also destruct an Object like this:

const {name,quantity} = { name: "apples", quantity: 2 };
console.log(name);
console.log(quantity);

// Result:
apples
2