给定一个JavaScript对象,

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

和字符串

"a.b"

我怎么把字符串转换成点符号呢

var val = obj.a.b

如果字符串只是'a',我可以使用obj[a]。但这个更复杂。我想应该有什么简单的方法,但现在想不起来了。


当前回答

这是我的实现

实现1

Object.prototype.access = function() {
    var ele = this[arguments[0]];
    if(arguments.length === 1) return ele;
    return ele.access.apply(ele, [].slice.call(arguments, 1));
}

实现2(使用数组reduce而不是slice)

Object.prototype.access = function() {
    var self = this;
    return [].reduce.call(arguments,function(prev,cur) {
        return prev[cur];
    }, self);
}

例子:

var myobj = {'a':{'b':{'c':{'d':'abcd','e':[11,22,33]}}}};

myobj.access('a','b','c'); // returns: {'d':'abcd', e:[0,1,2,3]}
myobj.a.b.access('c','d'); // returns: 'abcd'
myobj.access('a','b','c','e',0); // returns: 11

它也可以处理数组中的对象

var myobj2 = {'a': {'b':[{'c':'ab0c'},{'d':'ab1d'}]}}
myobj2.access('a','b','1','d'); // returns: 'ab1d'

其他回答

我从Ricardo Tomasi的回答中复制了以下内容,并进行了修改,以创建还不存在的子对象。它的效率有点低(更多的if和创建空对象),但应该很好。

它还允许我们做Object。Prop (obj, 'a.b', false)我们之前做不到。不幸的是,它仍然不允许我们赋值为undefined…我还不知道该怎么做。

/**
 * Object.prop()
 *
 * Allows dot-notation access to object properties for both getting and setting.
 *
 * @param {Object} obj    The object we're getting from or setting
 * @param {string} prop   The dot-notated string defining the property location
 * @param {mixed}  val    For setting only; the value to set
 */
 Object.prop = function(obj, prop, val){
   var props = prop.split('.'),
       final = props.pop(),
       p;

   for (var i = 0; i < props.length; i++) {
     p = props[i];
     if (typeof obj[p] === 'undefined') {
       // If we're setting
       if (typeof val !== 'undefined') {
         // If we're not at the end of the props, keep adding new empty objects
         if (i != props.length)
           obj[p] = {};
       }
       else
         return undefined;
     }
     obj = obj[p]
   }
   return typeof val !== "undefined" ? (obj[final] = val) : obj[final]
 }

使用数组缩减函数将获得/设置基于提供的路径。

我用a.b.c和a.b.2.c {a:{b:[0,1,{c:7}]}}测试了它,它既可以获取键,也可以将对象更改为设置值

function setOrGet(obj, path=[], newValue){ const l = typeof path === 'string' ? path.split('.') : path; return l.reduce((carry,item, idx)=>{ const leaf = carry[item]; // is this last item in path ? cool lets set/get value if( l.length-idx===1) { // mutate object if newValue is set; carry[item] = newValue===undefined ? leaf : newValue; // return value if its a get/object if it was a set return newValue===undefined ? leaf : obj ; } carry[item] = leaf || {}; // mutate if key not an object; return carry[item]; // return object ref: to continue reduction; }, obj) } console.log( setOrGet({a: {b:1}},'a.b') === 1 || 'Test Case: Direct read failed' ) console.log( setOrGet({a: {b:1}},'a.c',22).a.c===22 || 'Test Case: Direct set failed' ) console.log( setOrGet({a: {b:[1,2]}},'a.b.1',22).a.b[1]===22 || 'Test Case: Direct set on array failed' ) console.log( setOrGet({a: {b:{c: {e:1} }}},'a.b.c.e',22).a.b.c. e===22 || 'Test Case: deep get failed' ) // failed !. Thats your homework :) console.log( setOrGet({a: {b:{c: {e:[1,2,3,4,5]} }}},'a.b.c.e.3 ',22) )

我个人的建议。

除非没有别的办法,否则不要用这种东西!

我看到很多例子,人们用它来翻译json;你会看到locale('app。主页。欢迎')这样的函数。这太糟糕了。如果你已经在object/json中有数据;你知道路径。然后直接使用locale().app.首页示例。欢迎通过改变你的函数返回对象,你得到类型安全,自动完成,不容易出现错别字。

这是ninjagecko提出的我的扩展方案。

对我来说,简单的字符串表示法是不够的,所以下面的版本支持如下内容:

index(obj, 'data.accounts[0].address[0].postcode');

 

/**
 * Get object by index
 * @supported
 * - arrays supported
 * - array indexes supported
 * @not-supported
 * - multiple arrays
 * @issues:
 *  index(myAccount, 'accounts[0].address[0].id') - works fine
 *  index(myAccount, 'accounts[].address[0].id') - doesnt work
 * @Example:
 * index(obj, 'data.accounts[].id') => returns array of id's
 * index(obj, 'data.accounts[0].id') => returns id of 0 element from array
 * index(obj, 'data.accounts[0].addresses.list[0].id') => error
 * @param obj
 * @param path
 * @returns {any}
 */
var index = function(obj, path, isArray?, arrIndex?){

    // is an array
    if(typeof isArray === 'undefined') isArray = false;
    // array index,
    // if null, will take all indexes
    if(typeof arrIndex === 'undefined') arrIndex = null;

    var _arrIndex = null;

    var reduceArrayTag = function(i, subArrIndex){
        return i.replace(/(\[)([\d]{0,})(\])/, (i) => {
            var tmp = i.match(/(\[)([\d]{0,})(\])/);
            isArray = true;
            if(subArrIndex){
                _arrIndex =  (tmp[2] !== '') ? tmp[2] : null;
            }else{
                arrIndex =  (tmp[2] !== '') ? tmp[2] : null;
            }
            return '';
        });
    }

    function byIndex(obj, i) {
        // if is an array
        if(isArray){
            isArray = false;
            i = reduceArrayTag(i, true);
            // if array index is null,
            // return an array of with values from every index
            if(!arrIndex){
                var arrValues = [];
                _.forEach(obj, (el) => {
                    arrValues.push(index(el, i, isArray, arrIndex));
                })
                return arrValues;
            }
            // if array index is specified
            var value = obj[arrIndex][i];
            if(isArray){
                arrIndex = _arrIndex;
            }else{
                arrIndex = null;
            }
            return value;
        }else{
            // remove [] from notation,
            // if [] has been removed, check the index of array
            i = reduceArrayTag(i, false);
            return obj[i]
        }
    }

    // reduce with the byIndex method
    return path.split('.').reduce(byIndex, obj)
}

你可以用lodash。get

在安装(npm i lodash.get)后,像这样使用它:

const get = require('lodash.get');

const myObj = { 
    user: { 
        firstName: 'Stacky', 
        lastName: 'Overflowy',
        list: ['zero', 'one', 'two']
    }, 
    id: 123 
};

console.log(get(myObj, 'user.firstName')); // outputs Stacky
console.log(get(myObj, 'id'));             // outputs 123
console.log(get(myObj, 'user.list[1]'));   // outputs one

// You can also update values
get(myObj, 'user').firstName = 'John';

解决方案:

function deepFind(key, data){
  return key.split('.').reduce((ob,i)=> ob?.[i], data)
}

用法:

const obj = {
   company: "Pet Shop",
   person: {
      name: "John"
   },
   animal: {
      name: "Lucky"
   }
}

const company = deepFind("company", obj) 
const personName = deepFind("person.name", obj) 
const animalName = deepFind("animal.name", obj)