slice():從數組中返回選定(擷取）的元素，作為一個新數組。

參數（開始,結束但不包括）

const fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"];
const citrusSlice = fruits.slice(1, 3);
//Orange,Lemon

findIndex():方法將依據提供的測試函式，尋找陣列中符合的元素，並返回其 index（索引）。如果沒有符合的對象，將返回 -1 。

const array1 = [5, 12, 8, 130, 44];

const isLargeNumber = (element) => element > 13;

console.log(array1.findIndex(isLargeNumber));
// Expected output: 3

join():該方法通過連接數組

const elements = ['Fire', 'Air', 'Water'];

console.log(elements.join());
//"Fire,Air,Water"

console.log(elements.join(''));
//"FireAirWater"

console.log(elements.join('-'));
// "Fire-Air-Water"

split():分割字符串

const str = 'The quick brown fox jumps over the lazy dog.';
const strSplit=str.split('');
console.log('strSplit',strSplit)
//'strSplit' ["T","h","e"," ","q","u","i","c","k"," ","b","r","o","w","n"," ","f","o","x"," ","j","u","m","p","s"," ","o","v","e","r"," ","t","h","e"," ","l","a","z","y"," ","d","o","g","."]

includes():方法確定數組是否在其條目中包含某個值，返回true或 false

const array1 = [1, 2, 3];

console.log(array1.includes(2));
//  true

const pets = ['cat', 'dog', 'bat'];

console.log(pets.includes('cat'));
//  true

console.log(pets.includes('at'));
//  false

filter()：建立指定函式，由原陣列過濾指定函數產生新陣列

const words = ['spray', 'limit', 'elite', 'exuberant', 'destruction', 'present'];

const result = words.filter(word => 
    word.length > 6
);

console.log(result);
//Array ["exuberant", "destruction", "present"]

Filter去掉重複的元素

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let arr = ['B', 'A', 'E', 'C', 'A', 'F', 'G', 'E'];

let newArr = arr.filter( (element, index, arry)=> {
  //
  console.log('arry',arry)
 return arry.indexOf(element) === index;
});

console.log(newArr)

find()：回傳第一個滿足測試函式的元素值

const array1 = [5, 12, 8, 130, 44];
const found = array1.find(
                element => element > 10
            );
//console.log(found) 
//第一個滿足測試函式的元素值是：12
//12

Typescript union type

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let unionType: number | string  |  boonlean =12;
unionType:"12"; //string
unionType:true; //boonlean

//檢查類型 typeof
let checkType=88;
//=="引號"
if (typeof checkType=="number"   ){
    console.log(number)
}

unll & undefined

strick:true修改,嚴格模式

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let myNull=null;
myNull=undefined;

不能將其他類型轉為never

never應用場景:拋出異常

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function error( message:string ):never {
    throw new Error( message )
}

never應用場景:死循環

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function loop():never{
    while( true ){
    }
}

Typescript object & type

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let dataObject:{ name:string, age:number }= {
    name:'Jerry';
    age:31;
}
dataObject={
    name:'Hi';
    age:31;
}

複雜類型

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let complex: { data: number[ ] , myFunc: ( item:number )=>number[] }={
    data:[ 1, 2 ,33],
    myFunc:function( item:number )=>number[]{
        this.data.push( item );
        return this.data;
    }
}

type 生成類型

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type myType={ data: number[ ] , myFunc: ( item:number )=>number[] };

let complex2: myType={
    data:[ 1, 2 ,33],
    myFunc : function( item:number )=>number[]{
        this.data.push( item );
        return this.data;
    }
}

Typescript 函數相關類型

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function returnValue( ):string{
    return 'Hello';
}
console.log(returnValue( ))

Typescript 空

//空

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function sayHello( ):void{
 console.log( "sayHello" )
}

Typescript 參數類型

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function sumValue(value1:number,value2:number ){
    value1*value2
}
console.log( 2,3 ) //6

函數類型

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let myFunc;
myFunc=sayHello;
myFunc(); //sayHello
let towFunc:(a:number,b:number)=>number;
towFunc=sumValue;
 console.log( towFunc(4,5) ) //20