js 变量定义数组

// 定义一个空数组
let arr = [];

// 定义一个包含多个元素的数组
let fruits = ['apple', 'banana', 'cherry'];

// 定义一个包含不同数据类型的数组
let mixedArray = [1, 'hello', true, { name: 'John' }];

let fruits = ['apple', 'banana', 'cherry'];
console.log(fruits[0]); // 输出: apple
console.log(fruits[2]); // 输出: cherry

let fruits = ['apple', 'banana', 'cherry'];
console.log(fruits.length); // 输出: 3

let fruits = ['apple', 'banana', 'cherry'];
if (index >= 0 && index < fruits.length) {
    console.log(fruits[index]);
} else {
    console.log('Index out of bounds');
}

let mixedArray = [1, 'hello', true];
mixedArray.forEach(item => {
    if (typeof item === 'string') {
        console.log('String:', item);
    } else if (typeof item === 'number') {
        console.log('Number:', item);
    } else if (typeof item === 'boolean') {
        console.log('Boolean:', item);
    }
});

let numbers = [1, 2, 2, 3, 4, 4, 5];
let uniqueNumbers = [...new Set(numbers)]; // 使用Set去重
console.log(uniqueNumbers); // 输出: [1, 2, 3, 4, 5]

let uniqueNumbersFilter = numbers.filter((value, index, self) => {
    return self.indexOf(value) === index;
});
console.log(uniqueNumbersFilter); // 输出: [1, 2, 3, 4, 5]