Javascript - 链接到更大数组的值数组

Question

我正在使用 Javascript 并创建一个离线应用程序。

我有一个非常大的数组，超过 10mb。我需要保存用户已更改的数组中的元素，但将数组写入/读取到磁盘的速度太慢。

我想创建第二个数组，它只保存用户所做的更改，这样我就可以保存那个较小的数组，然后当我需要加载更改时，它可以将其更改镜像到大数组。

例如:

lib[x][1][y][6] = "no";
libVars[x][1][y][6] = "no";

libVars 将简单地保存 lib 中的元素更改，并且不会与大型数组 lib 的大小相同，因为用户只会与大型数组的一小部分进行交互。

显然这是行不通的，因为 libVars 与 lib 的结构不同，如果这样做也会占用大量内存(无论如何我是这么认为的!)

然后我想遍历 libVars 并在 libVars 中保存更改的相同元素点更新 lib。

有没有办法将某种类型的指针保存到 lib 中的某个位置，我可以将其与关联的元素值一起存储在 libVars 中？

任何帮助将不胜感激。

谢谢。

======================

我的大型阵列示例

var lib = [
[241,[[221119,"sample data","sample","no","no",131,"no"],
[221121,"sample2 data","sample2","no","no",146,"no"],
[221123,"sample3 data","sample3","no","no",28,"no"],
[221626,"sample4 data","sample4","no","no",26,"no"],
[221628,"sample5 data","sample5","no","no",88,"no"]]],
[330,[[305410,"2sample data","sample 2b","no","no",197,"no"],
[305412,"2sample 2 data","sample2 2b","no","no",147,"no"],
[305414,"3sample 2 data","sample3 2b","no","no",10,"no"] ... 

尝试 Z-Bone 发布的解决方案

我已经添加了 tempLib var，但我没有看到您最终如何更新实际的 lib 对象

Object.entries(libVars).forEach(([path, value]) => {

  var tempLib = lib;
  var pathParts = path.split('#');

  pathParts.forEach((pathPart, index) => {

  if (index == pathParts.length-1) {

    tempLib[pathPart] = value;

  } else {
    //I don't fully track what you are doing here. 
    //I assume you are building the array path, but to me it looks like
    // it's getting wiped out and not built upon?    
    tempLib = tempLib [pathPart];
  }
});
});

Answer 1

2019 年 1 月 28 日更新基于nomaam的测试数据

@nomaam 请检查以下代码段。我让它改变了 lib 数组中的任意路径。我选择的路径是这样的:lib[0][1][3][4]。您可以看到它最初如何返回值 "no"，然后在执行修改跟踪解决方案后返回值 "yes"。

// First Step: Original Data (lib)
var lib = [
[241,[[221119,"sample data","sample","no","no",131,"no"],
[221121,"sample2 data","sample2","no","no",146,"no"],
[221123,"sample3 data","sample3","no","no",28,"no"],
[221626,"sample4 data","sample4","no","no",26,"no"],
[221628,"sample5 data","sample5","no","no",88,"no"]]],
[330,[[305410,"2sample data","sample 2b","no","no",197,"no"],
[305412,"2sample 2 data","sample2 2b","no","no",147,"no"],
[305414,"3sample 2 data","sample3 2b","no","no",10,"no"]]]]

// Log initial value in arbitrary selection lib[0][1][3][4]
console.log(lib[0][1][3][4])

// Second Step: Pointer's object
var libVars = {}

// Example of changing a value via an artificial "pointer" to lib[0][1][3][4]
libVars['0#1#3#4'] = 'yes'; // original value is "no"

// Third Step: Run the modifier - update changes from libVars to lib
Object.entries(libVars).forEach(([path, value]) => {

  var tempLib = lib;
  var pathParts = path.split('#');
  
  pathParts.forEach((pathPart, index) => {
    
    if (index == pathParts.length - 1) {
      
      tempLib[pathPart] = value;
      
    } else {
      
      tempLib = tempLib[pathPart];
      
    }
  });
});


// Log the change fro lib
console.log(lib[0][1][3][4])

---

原始答案

如果我正确理解了您的挑战，从技术上讲，您可以持有一个对象，该对象将您要修改的属性的路径作为键，将修改后的值作为其值。

假设您的原始对象如下所示:

var lib = {a: {b: { c: { d: "yes"}}}}

您可以在备份对象中保留更改日志(例如，值从"is"更改为“否”)。它可能看起来像这样，用 . 标记嵌套属性。

var libVars = {};
libVars['a.b.c.d'] = "no";

然后当你想更新原始的大数组/值对象时，你可以这样做:

Object.entries(libVars).forEach(([path, value]) => {
    var tempLib = lib;
    // split by nesting indicator -> dot
    var pathParts = path.split('.');
    // iterate all parts of the path to the modified value
    pathParts.forEach((pathPart, index) => {
        if (index == pathParts.length-1) {
            // once you made your way to last index, update value
            tempLib[pathPart] = value;
        } else {
            tempLib = tempLib[pathPart];
        }
    })
})

console.log(lib); // outputs => {a: {b:{c: {d : "no"}}}}