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  • How about a "named true" and a "named true property"

How about a "named true" and a "named true property"

# Gray Zhang (8 years ago)

I don't really know how to name this feature, but I find it quite neccessary

In JavaScript land there are many functions with parameters of type boolean, and invocations to these functions do not have high readability, for example jQuery have a clone method with a parameter deep of type boolean, but when read a code like:

$.clone(sourceObject, true);

it's hard to understand what is that true stands for, a more unfamiliar API could make this more uncomfortable:

control.dispose(true); // does it mean "to remove DOM node or anything
else?"

In practice we can write some comment after a boolean parameter to explain what it is:

control.dispose(true /* removeNode */);

but it's a lot of work.

In this case I think we may introduce a handy syntax called "named true" which only transforms to the keyword true but have a custom name:

control.dispost(:removeNode);

Here a leading colon hints it is a "named true" so in parsing stage :removeNode simply becomes true, and we can have a false value with simply !:removeNode, it doesn't hit performance but notably increase readability

Boolean parameters is not good practice but I believe it is not eliminated nowadays and will never be eliminated, so a more friendly syntax could save a lot of time

Furthermore, there are also many functions accepting an options parameter including some "flag properties", flag properties are simple properties with a boolean value, a good example is the {silent: true} flag in many event related APIs.

Constructing an options object containing flag properties are not easy, we may repeat : true and : false many times, so with previously "named true", I think a "named true property" could help to save time:

model.set('foo', newValue, {:silent, :disableValidation, !:destroyOldValue})

Here :silent is simply parsed to silent: true and !:destroyOldValue is for destroyOldValue: false, it can save a large amount of code

All syntax here are just examples, not any propose to grammar

# Isiah Meadows (8 years ago)

Is defining a variable set to true not sufficient?

# G. Kay Lee (8 years ago)

Here you go...

var deep;

$.extend(!deep, object1, object2); // true

$.extend(!!deep, object1, object2); // false

What you're asking is essentially another !.

# Oriol Bugzilla (8 years ago)

As Isiah Meadows said, you can just use variables.

var removeNode = true;
control.dispose(removeNode);

var silent = true,
      disableValidation = true,
      destroyOldValue = false;
model.set('foo', newValue, {silent, disableValidation, destroyOldValue});
# Andy Earnshaw (8 years ago)

This is more a problem to be solved in API design and if you see such a method being introduced to libraries or specifications, you should raise your concerns with the author(s). Fortunately, Ecma-262 seems to avoid this pitfall by accepting objects-as-dictionaries, and most newer web APIs seem to be trending towards the same thing. Even jQuery has made an effort to do the same1.

You don't even need to use variables to avoid the boolean trap in third-party APIs, you can simply use strings:

$.clone(sourceObject, !!'deep'); // true $.clone(sourceObject, !'deep'); // false

This is more akin to the your :removeNode example and is something that a minifier or engine may optimise for you.