Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>There is a difference between instances and their constructors.</p> <p>When creating an object like <code>{a: 1}</code>, you're creating an instance of the <code>Object</code> constructor. <code>Object.prototype</code> is indeed available, and all functions inside that prototype are available:</p> <pre><code>var o = {a: 1}; o.hasOwnProperty === Object.prototype.hasOwnProperty; // true </code></pre> <p>But <code>Object.create</code> does something different. It creates an instance (an object), but inserts an additional prototype chain:</p> <pre><code>var o = {a: 1}; var p = Object.create(o); </code></pre> <p>The chain will be:</p> <pre><code>Object.prototype - o - p </code></pre> <p>This means that:</p> <pre><code>p.hasOwnProperty === Object.prototype.hasOwnProperty; // true p.a === o.a; // true </code></pre> <p>To get the prototype "under" an instance, you can use <code>Object.getPrototypeOf</code>:</p> <pre><code>var o = {a: 1}; var p = Object.create(o); Object.getPrototypeOf(p) === o; // true Object.getPrototypeOf(o) === Object.prototype; // true </code></pre> <p>(Previously, you could access an instance's prototype with <code>o.__proto__</code>, but this has been deprecated.)</p> <p>Note that you could also access the prototype as follows:</p> <pre><code>o.constructor === Object; // true </code></pre> <p>So:</p> <pre><code>o.constructor.prototype === Object.prototype // true o.constructor.prototype === Object.getPrototypeOf(o); // true </code></pre> <p>This fails for <code>Object.create</code>-created objects because they do not have a constructor (or rather, their constructor is <code>Object</code> and not what you passed to <code>Object.create</code> because the constructor function is absent).</p>
    singulars
    1. This table or related slice is empty.
    1. PODoes a new object in Javascript have a prototype property?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USpimvdb
    1. USpimvdb
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PODoes a new object in Javascript have a prototype property?
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COThanks for the detailed answer. The one thing I don't quite get is why `o.prototype` (which as you say above is an instance of the _Object_ constructor) returns `undefined`, and `Object.getPrototypeOf(o)` returns the prototype. Aren't they in theory the same thing and should be pointing to the same prototype object of o?
      singulars
      1. PO
      1. USdkugappi
    2. CO@Alex Nabokov: No - constructors have `.prototype` and instances have `Object.getPrototypeOf`. So with an object `o` there is `Object.prototype` (constructor) and `Object.getPrototypeOf(o)` (instance). These two *do* refer to the same thing.
      singulars
      1. PO
      1. USpimvdb
    3. COyou said "When creating an object like {a: 1}, you're creating an instance of the Object constructor". wouldn't it be more correct to say "... you're creating a new instance *using the Object constructor*"? I'm not trying to bash your answer but trying to understand this darn language Javascript.
      singulars
      1. PO
      1. USIan Durkan
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload