使用 Babel 和 JSPM 启用 ES2015 默认参数

Question

I'm setting up JSPM / Babel for the first time, and trying out a few ES6 features.

It seems only certain features work with the default transform, so I've tried to enable the ES2015 preset, using both package.json and the .babelrc file, as below:

"presets": ["es2015"]

This doesn't seem to have any effect.

I'm trying to add a default parameter to a function, so want to replace the following function

exports.width = function(x) {
    if (!arguments.length) return width;
    width = x;
    return this;
};

with

exports.width = function(x = width) {
    width = x;
    return this;
};

I keep getting a Uncaught SyntaxError: Unexpected token = error however.

I've installed the preset npm install babel-preset-es2015 --save-dev , as well as trying to install the individual plugin, but no dice.

Answer 1

Ah, so it seems JSPM will only transpile ES6 modules , so you need to pass a flag to any non ES6 modules to force it to transpile, so "format es6"; at the top of the file.

Which is odd as it was transpiling the lambda => functions but not the default params.