如何解决在 JavaScript 中将数据动态写入嵌套对象
我想将数据(以对象的形式)作为值动态写入嵌套在另一个对象中的对象;并动态创建键的名称(在循环内)。
我当前的代码如下所示:
data = {'x': 2,'y': 3}
master_obj = {'useless': {},'important': {}}
var block_ind = 0
let trials = 12
let trials_per_block = 4
for (trial_ind=0; trial_ind<trials; trial_ind++) {
// every 4 trials are in a new block
block_ind = trial_ind % trials_per_block == 0 ? trial_ind/trials_per_block : block_ind
master_obj['important']['block_0'+block_ind] = {}
master_obj['important']['block_0'+block_ind]['trial_0'+trial_ind] = data
}
console.log(master_obj)
useless: {}
important:
block_00:
trial_00: {x: 2,y:3}
trial_01: {x: 2,y:3}
trial_02: {x: 2,y:3}
trial_03: {x: 2,y:3}
block_01:
trial_04: {x: 2,y:3}
trial_05: {x: 2,y:3}
trial_06: {x: 2,y:3}
trial_07: {x: 2,y:3}
block_02:
trial_08: {x: 2,y:3}
trial_09: {x: 2,y:3}
trial_10: {x: 2,y:3}
trial_11: {x: 2,y:3}
感谢任何和所有帮助和建议!
解决方法
问题在于您不是在复制 data
,您只是在重复使用相同的对象。另一个问题是,当您尝试将另一个实例添加到现有块时,您会覆盖之前创建的对象。
如何复制它是一个潜在的复杂主题(请参阅 this question's answers),但是对于仅对其自身的可枚举属性进行浅表复制,您可以对对象使用扩展符号或 Object.assign
文字,请参阅下面的 ***
行:
const data = {"x": 2,"y": 3}
const master_obj = {"useless": {},"important": {}}
var block_ind = 0
let trials = 12
let trials_per_block = 4
const important = master_obj.important; // *** No need to repeat this
for (let trial_ind=0; trial_ind<trials; trial_ind++) {
// ^^^−−−− *** Declare your variables
// every 4 trials are in a new block
block_ind = trial_ind % trials_per_block == 0 ? trial_ind/trials_per_block : block_ind
// *** Only create this if it doesn't exist
if (!important["block_0"+block_ind]) {
important["block_0"+block_ind] = {}
}
important["block_0"+block_ind]["trial_0"+trial_ind] = {...data} // ***
}
console.log(master_obj)
另请注意,我在 const
和 data
上添加了 master_obj
。如果没有 let
、const
或 var
,您的代码将成为我所说的 The Horror of Implicit Globals 的牺牲品。一定要声明你的变量。 (我建议始终使用 const
或 let
,切勿使用 var
。)
就其价值而言,您可以使用 Math.floor(trial_ind / trials_per_block)
来确定块编号。这是加上几个模板文字和其他具有描述性名称的常量:
const data = {"x": 2,"y": 3};
const master_obj = {"useless": {},"important": {}};
const trials = 12;
const trials_per_block = 4;
const important = master_obj.important;
for (let trial_ind = 0; trial_ind < trials; ++trial_ind) {
// Every 4 trials are in a new block
const blockKey = `block_0${Math.floor(trial_ind / trials_per_block)}`;
const trialKey = `trial_0${trial_ind}`;
if (!important[blockKey]) {
important[blockKey] = {};
}
important[blockKey][trialKey] = {...data};
}
console.log(master_obj);
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