How do I access the current context inside a JavaScript function?

Question

If I have a function like this:

function doSomething(opt)
{
}

And I call it like this:

doSomething({a: 234, b: 567});

Is there a Javascript equivalent of the PHP extract() function so that I could do this:

function doSomething(opt)
{
    extract(opt);

    alert(a); // 234
    alert(b); // 567
}

The with() statement is not recommended any more and using the 'this' variable accesses the global scope - not the functions scope.

UPDATE:

Currently I'm doing the extraction manually like this:

function doSomething (opt)
{
    var a = opt.a,
        b = opt.b;
}

could declare your function like function doSomething({a, b}) — bamtheboozle
– bamtheboozle, Commented Oct 2, 2019 at 11:03
what you are looking for is called destructuring. you can also do it like { a, b } = opt — Chotala Paresh
– Chotala Paresh, Commented Oct 2, 2019 at 11:06
@DragoşPaulMarinescu That's very close to what I'm after - is it an ES6 thing? — Richard
– Richard, Commented Oct 2, 2019 at 11:07

Richard · Accepted Answer · 2019-10-02 11:33:45Z

3

You can use ES6 destructuring:

function doSomething({a, b})
{
    alert(a);
    alert(b);
}

Or

function doSomething(opt)
{
    const {a, b} = opt;
    alert(a);
    alert(b);
}

edited Oct 2, 2019 at 11:33

Richard

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answered Oct 2, 2019 at 11:09

Lior Hai

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1 Comment

Richard Over a year ago

Interesting note on this: I've now been looking up browser market share and IE11 still shows roughly 5-7% depending on the region. And with this browser not supporting destructuring (AFAIK) and my software being publicly usable on all types of website - I think I'll stick to the old fashioned method, like that shown in the question, in order to preserve BC. Thanks though.

Neil · Accepted Answer · 2019-10-03 03:02:16Z

1

Destructuring is one approach. Below is another approach.

JavaScript has a concept called Rest parameters.... collect rest of the parameters in an array. What does that mean?

function doSimething(...items) {
     items.forEach(() => {
        // you can do stuff with each of the items.
    });
}

You can call it doSimething(1); doSomething(3,5,h);

This approach could help you make the function be more generic and used in more places.

Additional information on JavaScript rest / spread parameters

edited Oct 3, 2019 at 3:02

answered Oct 2, 2019 at 11:57

Neil

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1 Comment

Richard Over a year ago

I think this would be best for what I was after - though due to browser share I've decided to stick with an ES5 compatible solution. Which is a shame because this would be perfect for what I want.

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