amd = requirejs (a -->async 异步模块加载, american module define )
cmd = seajs (china module define)
UMD = commonjs + amd (可怜的cmd)(先判断是否支持exports,然后是amd 实在不行就直接丢到window对象中)
esm = es6 module = import export
commonjs = cjs = module.exports ,同步加载, 一般用在nodejs 中
