JS实现99乘法表

// 99乘法表

/**
 * 正三角
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
 */
// i 代表行，j 代表列
// 随着行 i 增大，列 j 逐渐增大
for (let i = 1; i <= 9; i++) {
    let str = "";
    for (let j = 1; j <= i; j++) {
        str += `${j} * ${i} = ${i * j}\t`;
    }
    console.log(str);
}
console.log("===============");
/**
1 * 1 = 1
2 * 2 = 4       1 * 2 = 2
3 * 3 = 9       2 * 3 = 6       1 * 3 = 3
4 * 4 = 16      3 * 4 = 12      2 * 4 = 8       1 * 4 = 4
5 * 5 = 25      4 * 5 = 20      3 * 5 = 15      2 * 5 = 10      1 * 5 = 5
6 * 6 = 36      5 * 6 = 30      4 * 6 = 24      3 * 6 = 18      2 * 6 = 12      1 * 6 = 6
7 * 7 = 49      6 * 7 = 42      5 * 7 = 35      4 * 7 = 28      3 * 7 = 21      2 * 7 = 14      1 * 7 = 7
8 * 8 = 64      7 * 8 = 56      6 * 8 = 48      5 * 8 = 40      4 * 8 = 32      3 * 8 = 24      2 * 8 = 16      1 * 8 = 8
9 * 9 = 81      8 * 9 = 72      7 * 9 = 63      6 * 9 = 54      5 * 9 = 45      4 * 9 = 36      3 * 9 = 27      2 * 9 = 18      1 * 9 = 9
 */
// 随着行 i 增大，列 j 逐渐增大
for (let i = 1; i <= 9; i++) {
    let str = "";
    for (let j = i; j >= 1; j--) {
        str += `${j} * ${i} = ${i * j}\t`;
    }
    console.log(str);
}

console.log("===============");

/**
 * 倒三角
 * 1 * 1 = 1        2 * 1 = 2       3 * 1 = 3       4 * 1 = 4       5 * 1 = 5       6 * 1 = 6       7 * 1 = 7       8 * 1 = 8       9 * 1 = 9
                    2 * 2 = 4       3 * 2 = 6       4 * 2 = 8       5 * 2 = 10      6 * 2 = 12      7 * 2 = 14      8 * 2 = 16      9 * 2 = 18
                                    3 * 3 = 9       4 * 3 = 12      5 * 3 = 15      6 * 3 = 18      7 * 3 = 21      8 * 3 = 24      9 * 3 = 27
                                                    4 * 4 = 16      5 * 4 = 20      6 * 4 = 24      7 * 4 = 28      8 * 4 = 32      9 * 4 = 36
                                                                    5 * 5 = 25      6 * 5 = 30      7 * 5 = 35      8 * 5 = 40      9 * 5 = 45
                                                                                    6 * 6 = 36      7 * 6 = 42      8 * 6 = 48      9 * 6 = 54
                                                                                                    7 * 7 = 49      8 * 7 = 56      9 * 7 = 63
                                                                                                                    8 * 8 = 64      9 * 8 = 72
                                                                                                                                    9 * 9 = 81
 */
// 随着行 i 增大，列 j 逐渐减少
for (let i = 1; i <= 9; i++) {
    let str = "";
    // 每遍历一行，增加两个制表符
    for (let k = 1; k <= i; k++) {
        str += `\t\t`;
    }
    for (let j = i; j <= 9; j++) {
        str += `${j} * ${i} = ${i * j}\t`;
    }
    console.log(str);
}