with
Compile time with
for strict mode JavaScript
Installation
$ npm install with
Usage
var addWith = ; ;// => ';(function (console, a) {// console.log(a)// }("console" in obj ? obj.console :// typeof console!=="undefined" ? console : undefined,// "a" in obj ? obj.a :// typeof a !== "undefined" ? a : undefined));' ;// => ';(function (console, a) {// console.log(a)// }("a" in obj ? obj.a :// typeof a !== "undefined" ? a : undefined));'
API
addWith(obj, src[, exclude])
The idea is that this is roughly equivallent to:
with obj src;
There are a few differences though. For starters, assignments to variables will always remain contained within the with block.
e.g.
var foo = 'foo';with {} foo = 'bar';; // => This fails for compile time with but passes for native with var obj = foo: 'foo';with {} foo = 'bar';; // => This fails for compile time with but passes for native with
It also makes everything be declared, so you can always do:
if foo === undefined
instead of
if typeof foo === 'undefined'
This is not the case if foo is in exclude
. If a variable is excluded, we ignore it entirely. This is useful if you know a variable will be global as it can lead to efficiency improvements.
It is also safe to use in strict mode (unlike with
) and it minifies properly (with
disables virtually all minification).
Parsing Errors
with internally uses babylon to parse code passed to addWith
. If babylon throws an error, probably due to a syntax error, addWith
returns an error wrapping the babylon error, so you can
retrieve location information. error.component
is "src"
if the error is in the body or "obj"
if it's in the object part of the with expression. error.babylonError
is
the error thrown from babylon.
License
MIT