详解React项目中碰到的IE问题

if (!String.prototype.startsWith) {
 String.prototype.startsWith = function (search, pos) {
 return this.substr(!pos || pos < 0 ? 0 : +pos, search.length) === search
 }
}

'use strict'
/ eslint no-proto: 0 /
module.exports = Object.setPrototypeOf || ({ __proto__: [] } instanceof Array ? setProtoOf : mixinProperties)

function setProtoOf (obj, proto) {
 obj.__proto__ = proto
 return obj
}

function mixinProperties (obj, proto) {
 for (var prop in proto) {
 if (!obj.hasOwnProperty(prop)) {
  obj[prop] = proto[prop]
 }
 }
 return obj
}