无法覆盖javascript数组

Question

我需要监控结果。如果results.length增加，数组将被覆盖和保存。如果长度减少，则数组将被覆盖，但新值不会保存。

let playlists = [];
results = simpleMysqlQuery();
setinterval{
    update(playlists, results);
}

function update(playlists, results){
    if(playlists.length != results.length){
        playlists = reWritePlaylists(results, playlists);
    }
}

function reWritePlaylists(results, playlists){
   results.forEach(function(item, i, arr){
      playlists[i] = new Object();
      playlists[i]['id'] = results[i]['id'];
      playlists[i]['name'] = results[i]['name'];
   });
   if(playlists.length > results.length){
      playlists = playlists.slice(0, results.length);
   }
   return playlists;
}

Answer 1

我找到德威了！

function reWritePlaylists(results, playlists){
   playlists.splice(0, playlists.length);
   results.forEach(function(item, i, arr){
      playlists[i] = new Object();
      playlists[i]['id'] = results[i]['id'];
      playlists[i]['name'] = results[i]['name'];
   });
   return playlists;
}

Answer 2

使用slice并创建新数组时，新创建的数组不再是对原始数组的引用，因此update中的playlists参数不再引用与函数外部的playlists变量相同的数组实例。试试这个：

playlists = [];
results = simpleMysqlQuery();
setinterval{
    playlists = update(playlists, results);
}

function update(playlists, results){
    if(playlists.length != results.length){
        playlists = reWritePlaylists(results, playlists);
    }
    return playlists
}

function reWritePlaylists(results, playlists){
   results.forEach(function(item, i, arr){
      playlists[i] = new Object();
      playlists[i]['id'] = results[i]['id'];
      playlists[i]['name'] = results[i]['name'];
   });
   if(playlists.length > results.length){
      playlists = playlists.slice(0, results.length);
   }
   return playlists;
}

Answer 3

请按以下方式更新reWritePlaylists功能：

​

function reWritePlaylists(results, playlists){
   playlists.splice(0, results.length);
   results.forEach(function(item, i, arr){
      playlists[i] = new Object();
      playlists[i]['id'] = results[i]['id'];
      playlists[i]['name'] = results[i]['name'];
   });
   return playlists;
}

​