为什么webpack 打包会有这个说明，是因为用到了微软的__assign函数，
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var __assign = function() {
__assign = Object.assign || function __assign(t) {
for (var s, i = 1, n = arguments.length; i < n; i++) {
s = arguments[i];
for (var p in s) if (Object.prototype.hasOwnProperty.call(s, p)) t[p] = s[p];
}
return t;
};
return __assign.apply(this, arguments);
};
方案一：编译target不用es5，用es6。
方案二：【推荐】不用 { ...obj } 语法浅拷贝，改用Object.assign({}, obj)浅拷贝（相对__assign效率还高些）
参考： https://blog.csdn.net/kd_2015/article/details/123220478
