Hi,

This already has a Stage 0 proposal here:
https://github.com/tc39/proposal-bind-operator.

You can find all proposals at https://github.com/tc39/proposals in
(currently) three categories: That page itself, which lists proposals for
Stages 1, 2, and 3; and the linked lists of Stage 0 proposals, Inactive
proposals, and Finished proposals.

-- T.J. Crowder


On Sun, Feb 4, 2018 at 4:32 PM, Ludwig GUERIN <ludwig.guerin...@gmx.fr>
wrote:

> Sometimes, you need to pass a callback as a parameter of a function.
>
> Sometimes, you would like to pass in a method as the said parameter but
> you may encounter the common issue that the this keyword is not bound to
> the correct context anymore ; therefore you need to bind the correct
> context.
>
>
>
> Let's says that you have :
>
>    - a function `f` which receives a callback
>    -
>
>    and an object `obj` which has a method `method` which requires the `
>    this` keyword to be bound to `obj` in order to work properly as
>    intended.
>
>
>
> You will probably call `f` this way :
>
> `f(obj.method.bind(obj));`
>
>
>
> This is perfectly fine but sometimes can lead to a very large amount of
> extra "effort" for something that should not require that much "effort" and
> tends to take away a lot of space and clarity :`
>
> `f(obj.prop.method.bind(obj.prop));`
>
>
>
> My suggestion to solve this issue would be to use a new notation based
> around what C++ developers call the *scope resolution operator*, aka `::`.
>
> Here are details on how this should work :
>
>    -
>
>    `{object}` refers to an object (it can be either obj, or obj.method,
>    or obj.prop, etc...)
>    -
>
>    `{method}` refers to one of `{object}`'s methods (if `{object}` is obj
>    and we have `obj.method` then `{method}` would be `method`)
>    -
>
>    The "old-fashioned" way would look like `{object}.{method}.bind({
>    object})`
>    -
>
>    With this suggestion, it would look like `{object}::{method}`
>
>
>
> One way to implement such a functionality would be to establish a function
> autoBindContext which would guarantee the following properties :
>
>    -
>
>    `{object}::{method}` <=> `autoBindContext({object}.{method}, {object})`
>    -
>
>    Given any function/method `{fn}` (either `f` or `obj.method`), 
> `autoBindContext({fn},
>    null) === {fn}`
>    -
>
>    `{object}::{method}` <=> `({object})::{method}`
>    - const a = {object}::{method};
>    const b = {object}::{method};
>    a==b; //is true
>    a===b; //is true
>
>
>
> Below is one implementation of autoBindContext :
>
> ```javascript
>
> const autoBindContext = (method, context=null) => {
>   if(typeof method !== "function")
>     throw new TypeError("Can only bind the context of a function/method");
>
>   if(context === null)
>     return method; //Do not bind if the context is null
>
>   if(!(context instanceof Object))
>     throw new TypeError("Can only bind a function's/method's context to an 
> object");
>
>   const self = autoBindContext;
>   if(!self.cache.hasBinding(method, context))
>     self.cache.addBinding(method, context);
>
>   return self.cache.getBinding(method, context);
> }
> ‚Äč
> autoBindContext.cache = {
>   /***********************************\
>     binding: {context, method, bound}
>   \***********************************/
>     bindings: [],
>   lookForBinding(method, context=null){
>     return this.bindings.find(binding => {
>       return binding.context === context
>       && binding.method === method;
>     });
>   },
>   hasBinding(method, context=null){
>     return this.lookForBinding(method, context) !== undefined;
>   },
>   getBound(method, context=null){
>     if(this.hasBinding(method, context))
>         return this.lookForBinding(method, context).bound;
>
>     return null;
>   },
>   getBinding(method, context=null){
>     return this.getBound(method, context);
>   },
>   addBinding(method, context=null){
>     if(!this.hasBinding(method, context)){
>       this.bindings.push({
>         context,
>         method,
>         bound: method.bind(context)
>       });
>     }
>
>     return this;
>   }
> };
>
> ```
>
> _______________________________________________
> es-discuss mailing list
> es-discuss@mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
>
>
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