es6语法中最常见的9个函数介绍

下面web建站给大家介绍一下es6语法中最常见的9个函数介绍，它们分别是forEach、filter、map、concat、find、findIndex、includes、split、substr等。

forEach

let texts = "";
let arrs = ["Apple", "Orange", "Cherry", "Banana"];
arrs.forEach((item,index)=>{
  texts += item +  ',' ; 
});
console.log(texts)
// Apple,Orange,Cherry,Banana,

filter

let numbers = [15, 2, 50, 55, 90, 5, 4, 9, 10];
console.log(numbers.filter(number => number % 2 == 1)); 
// [15, 55, 5, 9]

map

let arr = [1, 2, 3];
let newArr = arr.map(num => num * 2);
console.log(newArr)
// [2, 4, 6]

concat

let str1 = "你好，";
let str2 = "中国！";
let str3 = str1.concat(str2); 
console.log(str3) //你好，中国！

find

const fruits = [
  { name: "apple", count: 10 },
  { name: "banana", count: 18 },
  { name: "mango", count: 3 }
];

const findMango = fruits.find(fruit =>fruit.name === "mango");
console.log(findMango) //{name: 'mango', count: 3}

findIndex

const fruits = [
  { name: "apple", count: 10 },
  { name: "banana", count: 18 },
  { name: "mango", count: 3 }
];

const findMango = fruits.findIndex(fruit =>fruit.name === "mango");
console.log(findMango) //2

includes

const birds = ["Birds", "peacock", "Dove", "Sparrow"];
console.log(birds.includes("Dove")); //true

split

let text = "Hello wo name china";
console.log(text.split(" ", 3));
//['Hello', 'wo', 'name']

substr

const test = "Hello wo name china, who are you.";
console.log(test.substr(0, 30));
//Hello wo name china, who are y