數組中所有方法（超詳細）

var str1 = "Hello ";
var str2 = "world!";
var n = str1.concat(str2);
Hello world!  輸出結果

• 如果數組中檢測到有一個元素不滿足，則整個表達式返回 false ，且剩餘的元素不會再進行檢測。
• 如果所有元素都滿足條件，則返回 true。

註意： every() 不會對空數組進行檢測。

註意： every() 不會改變原始數組。

例子：

var ages = [32, 33, 16, 40];

function checkAdult(age) {
    return age >= 18;
}

function myFunction() {
    document.getElementById("demo").innerHTML = ages.every(checkAdult);
}


false  輸出結果

var ages = [32, 33, 16, 40];

function checkAdult(age) {
    return age >= 18;
}

function myFunction() {
    document.getElementById("demo").innerHTML = ages.filter(checkAdult);
}
32,33,40 輸出結果

<button onclick="numbers.forEach(myFunction)">點我</button>
<p id="demo"></p>
 
<script>
demoP = document.getElementById("demo");
var numbers = [4, 9, 16, 25];
 
function myFunction(item, index) {
    demoP.innerHTML = demoP.innerHTML + "index[" + index + "]: " + item + "<br>"; 
}
</script>

輸出結果
index[0]: 4
index[1]: 9
index[2]: 16
index[3]: 25

var fruits = ["Banana", "Orange", "Apple", "Mango"];
var a = fruits.indexOf("Apple");

結果 2

var fruits = ["Banana", "Orange", "Apple", "Mango"];
var energy = fruits.join();
結果
Banana,Orange,Apple,Mango

var fruits = ["Banana", "Orange", "Apple", "Mango"];
var a = fruits.lastIndexOf("Apple");
結果 2

var numbers = [4, 9, 16, 25];

function myFunction() {
    x = document.getElementById("demo")
    x.innerHTML = numbers.map(Math.sqrt);
}
結果  2,3,4,5

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.pop();
返回  Banana,Orange,Apple

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.push("Kiwi")
結果輸出
Banana,Orange,Apple,Mango,Kiwi

var numbers = [65, 44, 12, 4];
 
function getSum(total, num) {
    return total + num;
}
function myFunction(item) {
    document.getElementById("demo").innerHTML = numbers.reduce(getSum);
}
輸出結果  125

var numbers = [65, 44, 12, 4];
 
function getSum(total, num) {
    return total + num;
}
function myFunction(item) {
    document.getElementById("demo").innerHTML = numbers.reduceRight(getSum);
}
輸出結果 125

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.reverse();
輸出結果
Mango,Apple,Orange,Banana

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.shift()
結果
Orange,Apple,Mango

var fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"];
var citrus = fruits.slice(1,3);
結果輸出  Orange,Lemon

var ages = [3, 10, 18, 20];

function checkAdult(age) {
    return age >= 18;
}

function myFunction() {
    document.getElementById("demo").innerHTML = ages.some(checkAdult);
}
輸出結果 true

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.sort();
輸出結果 Apple,Banana,Mango,Orange

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.splice(2,0,"Lemon","Kiwi");
輸出結果  Banana,Orange,Lemon,Kiwi,Apple,Mango

var d=new Date();
var n=d.toLocaleString();
輸出結果 2019/11/7 下午4:59:41

var d=new Date();
var n=d.toString();
Thu Nov 07 2019 17:00:09 GMT+0800 (中國標準時間)

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.unshift("Lemon","Pineapple");
fruits 將輸出：

Lemon,Pineapple,Banana,Orange,Apple,Mango

作者：高瑞廷

QQ：2419056691