javascript - 在每个循环中只有数组中的最后一个元素被连接起来

Question

问题:只有数组的最后一个元素在循环中的 finalOutput 中被连接

let listA = [
    [1, 2],
    [7, 8],
    [4, 5],
    [11, 12]
];
let listB = [
    ['x', 'y', 'z'],
    ['d', 'd', 'd'],
    ['f', 'y', 's']
];

let finalOutput = [];
for (let i = 1; i <= listA.length - 1; i++) {
    let dataIndx = 0;
    for (let item of listB) {
        if (item[1] !== 'd') {
            item[1] = listA[i][dataIndx];
            dataIndx++;
        }
    }
    finalOutput = finalOutput.concat(listB);
}

console.log('Undesired output:', finalOutput);

当前不需要的输出:

[
    ['x', '11', 'z'], ['d', 'd', 'd'], ['f', '12', 's'],
    ['x', '11', 'z'], ['d', 'd', 'd'], ['f', '12', 's'],
    ['x', '11', 'z'], ['d', 'd', 'd'], ['f', '12', 's'],
]

预期的 finalOutput 值为

[
    ['x', '7',  'z'], ['d', 'd', 'd'], ['f', '8',  's'],
    ['x', '4',  'z'], ['d', 'd', 'd'], ['f', '5',  's'],
    ['x', '11', 'z'], ['d', 'd', 'd'], ['f', '12', 's'],
]

Answer 1

这里的问题是您多次遍历 listB 并且每次都修改该列表(引用同一个数组)。由于数组是一个引用，最后一个将被记录在您的结果集中。尝试克隆 listB:

let listA= [[1,2],[7,8],[4,5],[11,12]];
let listB= [['x','y','z'],['d','d','d'],['f','y','s']]; 

let finalOutput = [];
for (let i = 1; i <= listA.length - 1; i++) {
  let dataIndx = 0;
  let listBB = listB.map(x => ([...x])); // "cloning an array of arrays"
  for(let item of listBB){
  
    if (item[1] !== 'd') {
         
         item[1] = listA[i][dataIndx];
         dataIndx++;
  }
  finalOutput = finalOutput.concat(listBB);
  }
    
}
console.log(finalOutput)