// x ** y
let squared = 2 ** 2;
// 等同于：2 * 2
let cubed = 2 ** 3;
// 等同于：2 * 2 * 2
// x **= y
let a = 2;
a **= 2;
// 等同于：a = a * a;
let b = 3;
b **= 3;
// 等同于：b = b * b * b;
npm install --save-dev babel-plugin-transform-exponentiation-operator
.babelrc（推荐）.babelrc
{
"plugins": ["transform-exponentiation-operator"]
}
babel --plugins transform-exponentiation-operator script.js
require("babel-core").transform("code", {
plugins: ["transform-exponentiation-operator"]
});