js高阶数组练习题

1.数组every()⽅法：给定⼀个包含数字的数组，检测其中的所有数字是否都⼩于 10

let arr = [3, 7, 9, 5, 2];
let val = arr.every(num => {  //num是参数
    return num < 10;
});
console.log(val);

2.数组filter()⽅法：给定⼀个包含字符串的数组，筛选出其中所有⻓度⼤于 5 的字符串，并返回⼀个新的数组

let string = ["2123333","13","342545","111","345"]
let val = string.filter((a)=>{
return a.length >= 5
})
console.log(val);

3.数组find()⽅法：给定⼀个包含学⽣对象的数组，查找出其中名字为 "Tom" 的学⽣对象，并返回该对象

let students = [
    { id: 1, name: "Alice" },
    { id: 2, name: "Bob" },
    { id: 3, name: "Tom" },
    { id: 4, name: "David" }
];
let val = students.find(student => student.name === "Tom");
console.log(val); 

4.数组findIndex()⽅法：给定⼀个包含学⽣对象的数组，查找出其中名字为 "Tom" 的学⽣对象的索引

let students = [
    { id: 1, name: "Alice" },
    { id: 2, name: "Bob" },
    { id: 3, name: "Tom" },
    { id: 4, name: "David" }
];
let val = students.findIndex(student => student.name === "Tom");
console.log(val); 

5.数组forEach()⽅法：给定⼀个包含数字的数组，使⽤forEach()⽅法将数组中的每个数字都乘以2

let num = [1, 2, 3, 4, 5];
num.forEach(num => {
    console.log(num * 2);
});

6.数组map()⽅法：给定⼀个包含数字的数组，使⽤map()⽅法将其中的每个数字都加上 10，并返回⼀个新的数组

let num = [1, 2, 3, 4, 5];
num.map(num => {
    console.log(num + 10);
});

7.数组reduce()⽅法：给定⼀个包含数字的数组，使⽤reduce()⽅法计算所有数字的和

let arr = [1, 2, 3, 4, 5];
let val = arr.reduce((a, b) => a + b, 0);
console.log(val);