JavaScript Double Colon (Bind Operator)

JavaScript double colon (bind operator)

No. The bind operator (spec proposal) comes in two flavours:

• Method extraction

  ::obj.method     ≡ obj.method.bind(obj)
  

• "virtual method" calls

  obj::function    ≡ function.bind(obj)
  obj::function(…) ≡ function.call(obj, …)
  

Neither of them feature partial application. For what you want, you should use an arrow function:

(...args) => this.handleStuff('stuff', ...args) ≡ this.handleStuff.bind(this, 'stuff')

What does :: (double colon) mean in JavaScript?

The :: is a proposed binding operator that desugars into a bound function:

::foo.bar
// becomes
foo.bar.bind(foo)

This is useful in React (and any other event handlers) because it means this will have the expected value (instance of the class) when the event handler is later invoked.

JavaScript double colon (bind operator)

No. The bind operator (spec proposal) comes in two flavours:

• Method extraction

  ::obj.method     ≡ obj.method.bind(obj)
  

• "virtual method" calls

  obj::function    ≡ function.bind(obj)
  obj::function(…) ≡ function.call(obj, …)
  

Neither of them feature partial application. For what you want, you should use an arrow function:

(...args) => this.handleStuff('stuff', ...args) ≡ this.handleStuff.bind(this, 'stuff')

What does ‘::’ (double colon) do in JavaScript?

Nothing. It is a syntax error.

>>> alert(42342::37438)
SyntaxError: missing ) after argument list

What does ‘::’ (double colon) do in javascript for events?

I've been able to find an obscure reference in some scanned manual from Microsoft Office Infopath 2003. It appears to be a JScript syntax:

a double colon is used as separator
between the script ID and the event
name

My guess is that's not part (or no longer part) of Internet explorer's ECMAScript implementation but it belongs (or used to belong) to Microsoft Office's implementation.

Babel is unable to parse double colon despite there being a babel config present

The Babel docs say that to use it, you need to:

(1) Install the plugin:

npm install --save-dev @babel/plugin-proposal-function-bind

(2) Add it to your Babel config:

{
  "plugins": ["@babel/plugin-proposal-function-bind"]
}

Or, you could go back to the old syntax without using Babel at all:

this.on('client:beforeCommand', (...args) => this.onBeforeCommand(...args));

What does two colons inside an angular expression {{::}} mean?

The {{::office.name}} syntax is Angular's One-Time binding, available since version 1.3

Here's a nice blog explaining it.

Double colons in function declaration in Javascript?

Thanks for everyone who looked into this.

Anyway, just as one could expect, not after five minutes after submitting the question, I found How to handle an ActiveX event in Javascript question about ActiveX callback handlers in IE, so it answers the main part of the question. As well, as the question that @outis has linked.

But I can't find any documentation on MSDN and that's troubling.

Conclusion: this is IE-specific ECMAScript extension for event handler declaration.

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