Intrusive

Overview

A collection of intrusive javascript changes. Don't use in libraries, only use in apps.

npm install intrusive

Then in the start of your app

require('intrusive')

Documentation

(More coming soon, hopefully)

Soak babel plugin

The soak babel plugin introduces a new unary prefix operator, +~, which automatically adds existence guards to its argument. The null check applies recursively to an entire member chain. In CoffeeScript terms, this is equivalent to replacing every . with ?., every subscript [... with ?[... and every function call fn(... with fn?(....

In other words, +~foo.bar().baz will check that foo exists, that foo.bar exists, and that foo.bar() exists. If any of those evaluate to null or undefined, the expression will return undefined (it will not return null even if, for example foo is null). If all of them do exist, then the result will be the same as foo.bar().baz (including null).

If these property accesses and methods cause side effects, then it is guaranteed that exactly the same side effects will occur when using +~. Of course, in the case that a null check fails, only the side effects up to that point will occur.

For example:

var count = 0;
var x = {
    y: function () {
        count++,
        return {z: 'tada!'},
    },
};

console.log(+~x.y().z); // --> tada!
console.log(count);     // --> 1

This is also the case for computed properties/indexes. For example:

var index = 0;
var arr = [{x: 'cat'}];

console.log(+~arr[index++].x) // --> cat
console.log(index)            // --> 1

Non-guarded constructions

Note, however, that neither function arguments, nor subscript property names are null checked. For example

var x = {}, foo = null;
+~x[foo.bar]; // --> error

You can, of course, nest the +~ operator, like so:

+~x[+~foo.bar]; // --> undefined

Finally, note that while function calls are guarded, the +~ operator does not guard against calling non-functions. This will still throw an error:

var x = {y: 'z'};
+~x.y(); // --> error (x.y is not a function)

Runtime requirements

The generated code requires that the function __soakNoop be defined in scope. The file 'babel-plugins/soak-runtime.js' defines this globally, but you can also define it manually. It is assumed to be an empty function, and to return nothing.