Array
in Programming on Javascript
Javascript ES6,ES7,ES8
Array
Array.of
const friends = ["Euido", "Josh", "Paul", "Tidermann"];
const friends = Array.of("Euido", "Josh", "Paul", "Tidermann");
// two codes are same.
Array.from
Let’s attach Event listner to each button
Example 1)
<body>
<button>1</button>
<button>2</button>
<button>3</button>
<button>4</button>
<button>5</button>
<button>6</button>
<button>7</button>
<button>8</button>
<button>9</button>
<button>10</button>
</body>
const buttons = document.querySelectorAll("button");
console.log(buttons);
// result : we can get NodeList. Not array.
Example 2)
<body>
<button class="btn">1</button>
<button class="btn">2</button>
<button class="btn">3</button>
<button class="btn">4</button>
<button class="btn">5</button>
<button class="btn">6</button>
<button class="btn">7</button>
<button class="btn">8</button>
<button class="btn">9</button>
<button class="btn">10</button>
</body>
const buttons = document.getElementByClassName("btn");
console.log(buttons);
// result : we can get HTMLCollection. Not array.
these are called “array-like object” not “array”
and “array-like object” has not forEach function not like “array”
so…. we should change the type as below.
Array.from(buttons).forEach(button => {
button.addEventListener("click",() => console.log("I ve been clicked"));
})
Various Array functions
1.find
const friends = [
"leeeuido@gmail.com"
"leeeuido@naver.com"
"leeeuido@daum.net"
"mark@hanmail.com"
"paul@lycos.com"
];
const target = friends.find(friend => friend.include("@gmail.com"));
// find try to execute friend.include("gmail.com") for each element of array.
// if they return first element which match with the condition.
console.log(target);
//result : leeeuido@gmail.com
2.index
const friends = [
"leeeuido@gmail.com"
"leeeuido@naver.com"
"leeeuido@daum.net"
"mark@hanmail.com"
"paul@lycos.com"
];
const target = friends.findIndex(friend => friend.include("@gmail.com"));
// find try to execute friend.include("gmail.com") for each element of array.
// if they return index of the first element which match with the condition.
console.log(target);
//result : 0
3.fill
const friends = [
"leeeuido@gmail.com"
"leeeuido@naver.com"
"leeeuido@daum.net"
"mark@hanmail.com"
"paul@lycos.com"
];
friends.fill("*".repeat("5"),1,2);
//fill(value:string, start?:number, end?:number)
console.log(friends);
//result : ["leeeuido@gmail.com", "*****", "*****", "mark@hanmail.com", "paul@lycos.com"]
4.include
const friends = [
"leeeuido@gmail.com"
"leeeuido@naver.com"
"leeeuido@daum.net"
"mark@hanmail.com"
"paul@lycos.com"
];
console.log(friends.include("leeeuido@daum.net"));
include return true or false