Question

更新：我自己想出了解决方案。而不是执行下面的解决方案，一个更简单的解决方案是

代码源

let trUp =（和弦）=> {

让index = arr.indexOf（chord）; 返回arr.IndedOf（index）-1;

}

Answer 1

您可以使用数组，并使用reminder operator %通过调整数组的长度来寻找索引和增量。

function up(note) {
    return notes[(notes.indexOf(note) + 1) % notes.length];
}

var notes = ['A', 'A#', 'B', 'C', 'C#', 'D', 'D#', 'E', 'F', 'F#', 'G', 'G#'];

console.log(up('C'));

Answer 2

稍长的版本，可让您上下移调单个和弦或一组和弦...

const chordMap = ['A','A#','B','C','C#','D','D#','E','F','F#','G','G#'];

定义一些函数将和弦向上或向下移动1并返回结果

function chordUp(chord) {
    let index = chordMap.indexOf(chord) + 1;
    if (index >= chordMap.length) index = 0;
    return chordMap[index];
}

function chordDown(chord) {
    let index = chordMap.indexOf(chord) - 1;
    if (index < 0) index = chordMap.length - 1;
    return chordMap[index];
}

然后函数将整个和弦数组上移或下移1并将结果作为数组返回

function transposeUp(input) {
    let output = [];
    for (let i = 0; i < input.length; i++) {
        let chord = input[i];
        output.push(chordUp(chord));
    }
    return output;
}

function transposeDown(input) {
    let output = [];
    for (let i = 0; i < input.length; i++) {
        let chord = input[i];
        output.push(chordDown(chord));
    }
    return output;
}

最后，您可以像这样使用它...

let chords = ['A', 'G#', 'B', 'C#',  'A#', 'G'];

let transposedUp = transposeUp(chords); // [ "A#", "A", "C", "D", "B", "G#" ];
let transposedDown = transposeDown(chords) // [ "G#", "G", "A#", "C", "A", "F#" ];

我的解决方案需要纠正什么才能使其正常工作

2 个答案: