parse from string as object path

Question

Let's say I have a form, and I want to check what inputs has been declared in the form, so I do something like this:

let inputs = {};

['first_name', 'last_name', ...].forEach(name => {
    let input = document.querySelector(`input[name="${name}"]`);

    if (input !== undefined)
        inputs = Object.assign(inputs, {[input.getAttribute('name')]: input.value});
}

In this case, so far so good.

But what if have some inputs called ['name.first', 'name.last']? then, it will store the data to an object like this:

{name.first: '...', name.last: '...'}.

and not like this: (which is my desired result)

{
    name: {
        first: '...',
        last: '...'
    }
}

How can I tell JavaScript to parse it as an object path instead of a key string?

Your first example would be better written with forEach or even reduce as you are not actually performing a map. I'm also curious as to why you use a fixed array of names to filter results? Perhaps you could explain a little more about what you are doing? — Xotic750
– Xotic750, Commented Dec 18, 2016 at 11:18
you were right, using map instead of forEach wasn't smart at all. It was a mistake. — Eliya Cohen
– Eliya Cohen, Commented Dec 18, 2016 at 11:34

Amit · Accepted Answer · 2016-12-18 11:20:12Z

I would use a custom assigning function.

An object can use any string as key, so "a.b" is valid.

Here is an example of an assign function:

function assign(obj, key, value) {
    let keys = key.split(".");
    let last = keys.pop();
    keys.forEach(key => {
        if(!obj[key])
            obj[key] = {};
        obj = obj[key];
    });

    obj[last] = value;
}

let obj = {};
assign(obj, "name.first", "hey");
assign(obj, "name.last", "bye");

console.log(obj);

Bonus recomendation: you can use it as a global form handler, if you use the same format to all forms.

function formHandler(form) {
    let obj = {};
    form.querySelectorAll("input, select").forEach(elem => assign(obj, elem.name, elem.value));
    return obj;
}

IAmDranged · Accepted Answer · 2016-12-18 11:05:36Z

Something like that?

  var obj = {
      'prop': 'value',
      'nested.prop1': 'value1',
      'nested.prop2': 'value2',
      'renested.prop1': 'value1',
      'renested.prop2': 'value2',    
      'nested.prop3': 'value3',
  }

  function deconcatProp(obj){

      var idx;
      var key;

      for(var prop in obj){
          if((idx = prop.indexOf('.')) > 0){
              key = prop.substring(0, idx);
              if(!obj[key]) {
                  obj[key] = {
                  };
              }
              obj[key][prop.substring(idx + 1, prop.length)] = obj[prop];
              delete obj[prop];
          }
      }

  }

 deconcatProp(obj);

Xotic750 · Accepted Answer · 2016-12-18 12:31:11Z

Using the same principle as the other answers (split, test and create) for creating paths, but demonstrates an alternative of your filtering example (as mentioned in my comment).

const wanted = ['name.first', 'name.second', 'name.last'];
const result = Array.from(document.querySelectorAll('input'))
  .filter(input => wanted.includes(input.name))
  .reduce((a, input) => {
    const paths = input.name.split('.');
    const key = paths.pop();
    let current = a;
    paths.forEach(path => current = current[path] ?
      current[path] :
      current[path] = Object.create(null));
    current[key] = input.value;
    return a;
  }, Object.create(null));

console.log(result);

<input name="name.first" value="Eliya" />
<input name="name.middle" value="Wibble" />
<input name="name.last" value="Cohen" />

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