babel-plugin-const-enum v1.2.0
babel-plugin-const-enum ·
Transform TypeScript
const
enums
Install
Using npm:
npm install --save-dev babel-plugin-const-enum
or using yarn:
yarn add babel-plugin-const-enum --dev
Usage
You are most likely using
@babel/preset-typescript
or
@babel/plugin-transform-typescript
along with this plugin.
If you are using @babel/preset-typescript
, then nothing special needs to be
done since
plugins run before presets.
If you are using @babel/plugin-transform-typescript
, then make sure that
babel-plugin-const-enum
comes before
@babel/plugin-transform-typescript
in the plugin array so that
babel-plugin-const-enum
runs first.
This plugin needs to run first to transform the const enum
s into code that
@babel/plugin-transform-typescript
allows.
.babelrc
{
"plugins": ["const-enum", "@babel/transform-typescript"]
}
transform: removeConst
(default)
Removes the const
keyword to use regular enum
.
Can be used in a slower dev build to allow const
, while prod still uses tsc
.
See babel#6476.
// Before:
const enum MyEnum {
A = 1,
B = A,
C,
D = C,
E = 1,
F,
G = A * E,
H = A ** B ** C,
I = A << 20
}
// After:
enum MyEnum {
A = 1,
B = A,
C,
D = C,
E = 1,
F,
G = A * E,
H = A ** B ** C,
I = A << 20
}
.babelrc
{
"plugins": [
"const-enum"
]
}
Or Explicitly:
.babelrc
{
"plugins": [
[
"const-enum",
{
"transform": "removeConst"
}
]
]
}
transform: constObject
Transforms into a const
object literal.
Can be further compressed using Uglify/Terser to inline enum
access.
See babel#8741.
// Before:
const enum MyEnum {
A = 1,
B = A,
C,
D = C,
E = 1,
F,
G = A * E,
H = A ** B ** C,
I = A << 20
}
// After:
const MyEnum = {
A: 1,
B: 1,
C: 2,
D: 2,
E: 1,
F: 2,
G: 1,
H: 1,
I: 1048576
};
.babelrc
{
"plugins": [
[
"const-enum",
{
"transform": "constObject"
}
]
]
}
Troubleshooting
SyntaxError
You may be getting a SyntaxError
because you are running this plugin on
non-TypeScript source. You might have run into this problem in react-native
,
see:
babel-plugin-const-enum#2
babel-plugin-const-enum#3
This seems to be caused by react-native
transpiling
flow
code in node_modules
.
To fix this issue, please use
babel-preset-const-enum
to only run babel-plugin-const-enum
on TypeScript files.
If you wish to fix the issue manually, check out the
solution in babel-plugin-const-enum#2.