@babel/plugin-transform-private-methods
This plugin is included in @babel/preset-env, in ES2022
History
| Version | Changes |
|---|---|
v7.3.0 | Support private accessors (getters and setters) |
v7.2.0 | Initial Release |
Example
classCounterextendsHTMLElement{
#xValue =0;
get#x(){
returnthis.#xValue;
}
set#x(value){
this.#xValue= value;
window.requestAnimationFrame(this.#render.bind(this));
}
#clicked(){
this.#x++;
}
}
Installation
- npm
- Yarn
- pnpm
- Bun
npm install @babel/plugin-transform-private-methods --save-dev
yarn add @babel/plugin-transform-private-methods --dev
pnpm add @babel/plugin-transform-private-methods --save-dev
bun add @babel/plugin-transform-private-methods --dev
Usage
With a configuration file (Recommended)
Without options:
{
"plugins":["@babel/plugin-transform-private-methods"]
}
With options:
{
"plugins":[["@babel/plugin-transform-private-methods",{"loose":true}]]
}
Via CLI
$ babel --plugins @babel/plugin-transform-private-methods script.js
Via Node API
require("@babel/core").transformSync("code",{
plugins:["@babel/plugin-transform-private-methods"],
});
Options
loose
boolean, defaults to false.
The loose mode configuration setting must be the same as @babel/plugin-transform-class-properties.
When true, private methods will be assigned directly on its parent
via Object.defineProperty rather than a WeakSet. This results in improved
performance and debugging (normal property access vs .get()) at the expense
of potentially leaking "privates" via things like Object.getOwnPropertyNames.
Consider migrating to the top level privateFieldsAsProperties assumption.
{
"assumptions":{
"privateFieldsAsProperties":true,
"setPublicClassFields":true
}
}
Note that both privateFieldsAsProperties and setPublicClassFields must be set to true.
Let's use the following as an example:
classFoo{
constructor(){
this.publicField=this.#privateMethod();
}
#privateMethod(){
return42;
}
}
By default, this becomes:
varFoo=functionFoo(){
"use strict";
babelHelpers.classCallCheck(this,Foo);
_privateMethod.add(this);
this.publicField= babelHelpers
.classPrivateMethodGet(this, _privateMethod, _privateMethod2)
.call(this);
};
var _privateMethod =newWeakSet();
var_privateMethod2=function_privateMethod2(){
return42;
};
With { privateFieldsAsProperties: true }, it becomes:
varFoo=functionFoo(){
"use strict";
babelHelpers.classCallCheck(this,Foo);
Object.defineProperty(this, _privateMethod,{
value: _privateMethod2,
});
this.publicField= babelHelpers
.classPrivateFieldLooseBase(this, _privateMethod)
[_privateMethod]();
};
var _privateMethod = babelHelpers.classPrivateFieldLooseKey("privateMethod");
var_privateMethod2=function_privateMethod2(){
return42;
};
You can read more about configuring plugin options here