1. JavaScript 基础

  2. 函数进阶

  3. 深入数据和类型

  4. 运算符

  5. 浏览器存储

  6. Document

  7. Web API

  8. 事件

  9. 错误处理

  10. 异步编程

  11. 网络请求

  12. 模块

  13. 练习

  14. 实例

  15. 工具与规范

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查看答案的输出时先按 F12 将控制台窗口打开。

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  1. 打印从 1 至 10 的数字。

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for (let i = 1; i <= 10; i++) {
    console.log(i)
}

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  1. 打印小于等于 100 的正奇数。

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for (let i = 1; i <= 100; i += 2) {
    console.log(i)
}

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  1. 打印 7 的乘法表,如下:
1 * 7 = 7
2 * 7 = 14
3 * 7 = 21
4 * 7 = 28
5 * 7 = 35
6 * 7 = 42
7 * 7 = 49
8 * 7 = 56
9 * 7 = 63

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for (let i = 1; i <= 100; i += 2) {
    console.log(i)
}

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  1. 打印 9 * 9 乘法表,如下:
1 * 1 = 1    
1 * 2 = 2    2 * 2 = 4    
1 * 3 = 3    2 * 3 = 6    3 * 3 = 9    
1 * 4 = 4    2 * 4 = 8    3 * 4 = 12    4 * 4 = 16    
1 * 5 = 5    2 * 5 = 10    3 * 5 = 15    4 * 5 = 20    5 * 5 = 25    
1 * 6 = 6    2 * 6 = 12    3 * 6 = 18    4 * 6 = 24    5 * 6 = 30    6 * 6 = 36    
1 * 7 = 7    2 * 7 = 14    3 * 7 = 21    4 * 7 = 28    5 * 7 = 35    6 * 7 = 42    7 * 7 = 49    
1 * 8 = 8    2 * 8 = 16    3 * 8 = 24    4 * 8 = 32    5 * 8 = 40    6 * 8 = 48    7 * 8 = 56    8 * 8 = 64    
1 * 9 = 9    2 * 9 = 18    3 * 9 = 27    4 * 9 = 36    5 * 9 = 45    6 * 9 = 54    7 * 9 = 63    8 * 9 = 72    9 * 9 = 81

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$$jsdemo$$
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for (let i = 1; i < 10; i++) {
    let row = ""
    for (let j = 1; j <= i; j++) {
        row += `${j} * ${i} = ${j * i}    `
    }
    console.log(row)
}

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  1. 计算从 1 到 10 的的总和。

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let sum = 0
for (let i = 1; i <= 10; i++) {
    sum += i
}
console.log(sum)

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  1. 计算 10! (阶乘)的值。

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let prod = 1
for (let i = 1; i <= 10; i++) {
    prod *= i
}
console.log(prod)

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  1. 写一个函数,判断给定的数是否是质数,如下:
function testPrime(n) {
    // 测试质数
    // ......
}

console.log(testPrime(17)) // true
console.log(testPrime(4)) // false
console.log(testPrime(1)) // false

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function testPrime(n) {
    // 测试质数
    if (n < 2) {
        return false
    }

    for (let i = 2; i < n; i++) {
        if (n % i == 0) {
            return false
        }
    }
    return true
}

console.log(testPrime(17)) // true
console.log(testPrime(4)) // false
console.log(testPrime(1)) // false

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  1. 写个一个函数,从数组中删除指定的元素,如下:
function deleteElement(arr, ele) {
    // 补全这里
}
let arr = [1, 3, 5, 3, 6]
arr = deleteElement(arr, 3)

console.log(arr) // [1, 5, 6]

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function deleteElement(arr, ele) {
    for (let i = 0; i < arr.length; i++) {
        if (arr[i] == ele) {
            arr.splice(i, 1) //Delete element from array
        }
    }
    return arr
}
let arr = [1, 3, 5, 3, 6]
arr = deleteElement(arr, 3)

console.log(arr) // [1, 5, 6]

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