动态访问Javascript中的数组 [英] dynamic access to an array in Javascript

问题描述

也许已经有了解决方案，但我找不到.我尝试动态访问多维数组中的不同插槽，但是面临着不同深度的挑战.基本上看起来像这样:

Maybe there is already a solution, but I can't find it. I try to access different slots in a multi dimensional array dynamical but with the challenge of different depths. Basically, it looks like this:

var source = [];
source['lvl1'] = [];
source['lvl1']['lvl2a'] = [];
source['lvl1']['lvl2a']['lvl3'] = "ping";
source['lvl1']['lvl2b'] = "pong";

如果深度是固定的，我可以这样编写代码:

If the depth is fix, I could write code like this:

var path1 = ["lvl1","lvl2a","lvl3"];
var path2 = ["lvl1","lvl2b"];

console.log(source[path1[0]][path1[1]][path[2]]); // => ping
console.log(source[path2[0]][path2[1]]); // => pong

我的问题是编写适用于两种变体的代码.这将起作用:

My problem is to write a code that works for both variants. This would work:

switch(path.length)
{
  case 1:
    console.log(source[path[0]]);
    break;
  case 2: 
    console.log(source[path[0]][path[1]]);
    break;
  case 3:
    console.log(source[path[0]][path[1]][path[2]]);
    break;
}

但这既不高效也不优雅.有没有其他的解决方案，例如与某种循环一起工作?！?

But this is neither efficient nor elegant. Has somebody another solution that works for example with some kind of loop?!?

谢谢托马斯

推荐答案

您可以从路径(经过测试的代码)中获取值:

You can get a value from a path (tested code):

var getValue = function(path, context) {
    if ('object' !== typeof context) {
        throw new Error('The context must be an object; "' + typeof context + '" given instead.');
    }
    if ('string' !== typeof path) {
        throw new Error('The path must be a string; "' + typeof context + '" given instead.');
    }

    var fields = path.split('.'),
        getValueFromFields = function(fields, context) {
            var field = fields.shift();

            if (0 === fields.length) {
                return context[field];
            }

            if ('object' !== typeof context[field]) {
                throw new Error('The path "' + path + '" has no value.');
            }

            return getValueFromFields(fields, context[field]);
        }
    ;

    return getValueFromFields(fields, context);
}

var source = [];
source['lvl1'] = [];
source['lvl1']['lvl2a'] = [];
source['lvl1']['lvl2a']['lvl3'] = "ping";
source['lvl1']['lvl2b'] = "pong";

console.log(getValue('lvl1.lvl2a.lvl3', source)); // ping
console.log(getValue('lvl1.lvl2b', source));      // pong

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