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babel-plugin-transform-es2015-block-scoping
Compile ES2015 block scoping (const and let) to ES5
Installation
npm install --save-dev babel-plugin-transform-es2015-block-scoping
Usage
Via .babelrc (Recommended)
.babelrc
Without options:
{
"plugins": ["transform-es2015-block-scoping"]
}
With options:
{
"plugins": [
["transform-es2015-block-scoping", {
"throwIfClosureRequired": true
}]
]
}
Via CLI
babel --plugins transform-es2015-block-scoping script.js
Via Node API
require("babel-core").transform("code", {
plugins: ["transform-es2015-block-scoping"]
});
Options throwIfClosureRequired
In cases such as the following it's impossible to rewrite let/const without adding an additional function and closure while transforming:
for (let i = 0; i < 5; i++) {
setTimeout(() => console.log(i), 1);
}
In extremely performance-sensitive code, this can be undesirable. If "throwIfClosureRequired": true is set, Babel throws when transforming these patterns instead of automatically adding an additional function.