以点表示法转换字符串以获取对象引用 [英] Convert string in dot notation to get the object reference

问题描述

在javascript中考虑此对象，

Consider this object in javascript,

var obj = { a : { b: 1, c: 2 } };

给定字符串obj.ab如何获取此引用的对象，以便我可能改变它的价值？即我希望能够做类似的事情

given the string "obj.a.b" how can I get the object this refers to, so that I may alter its value? i.e. I want to be able to do something like

obj.a.b = 5;
obj.a.c = 10;

其中obj.a.b& obj.a.c是字符串（不是obj引用）。
我遇到了这篇文章我可以在哪里获得点符号字符串引用obj的值，但我需要的是一种可以获取对象本身的方法？

where "obj.a.b" & "obj.a.c" are strings (not obj references). I came across this post where I can get the value the dot notation string is referring to obj but what I need is a way I can get at the object itself?

对象的嵌套可能比这更深。即可能

The nesting of the object may be even deeper than this. i.e. maybe

var obj = { a: { b: 1, c : { d : 3, e : 4}, f: 5 } }

推荐答案

要获取该值，请考虑：

To obtain the value, consider:

function ref(obj, str) {
    str = str.split(".");
    for (var i = 0; i < str.length; i++)
        obj = obj[str[i]];
    return obj;
}

var obj = { a: { b: 1, c : { d : 3, e : 4}, f: 5 } }
str = 'a.c.d'
ref(obj, str) // 3

或以更奇特的方式，使用减少：

or in a more fancy way, using reduce:

function ref(obj, str) {
    return str.split(".").reduce(function(o, x) { return o[x] }, obj);
}

在javascript中无法返回对象成员的可分配引用我必须使用如下函数：

Returning an assignable reference to an object member is not possible in javascript, you'll have to use a function like the following:

function set(obj, str, val) {
    str = str.split(".");
    while (str.length > 1)
        obj = obj[str.shift()];
    return obj[str.shift()] = val;
}

var obj = { a: { b: 1, c : { d : 3, e : 4}, f: 5 } }
str = 'a.c.d'
set(obj, str, 99)
console.log(obj.a.c.d) // 99

或使用上面给出的 ref 获取对包含对象的引用，然后应用 [] 运算符：

or use ref given above to obtain the reference to the containing object and then apply the [] operator to it:

parts = str.split(/\.(?=[^.]+$)/)  // Split "foo.bar.baz" into ["foo.bar", "baz"]
ref(obj, parts[0])[parts[1]] = 99

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