我有这样的用例：
const language = "en"/"jp"/null/undefined;
// Here is my language value that I get from server
// It could be "en","jp",null or undefined
// I set language value into localStorage
localStorage.setItem("language",language)
// Somewhere I get language from localStorage
localStorage.getItem("language");
我的问题是，当我从localStorage获取的值为language或null的{{1}}时。我收到的结果是一个字符串（undefined或"null"）
在当前代码中，我像这样检查手册：
"undefined"但是，我知道这是一个不好的方法。因此，有什么方法可以快速检查我的案件吗？
感谢您的帮助
请使用JSON解析器
import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import { FormsModule,ReactiveFormsModule } from '@angular/forms';
import { Routes,RouterModule } from '@angular/router';
import { IonicModule } from '@ionic/angular';
import { PurchaseorderMaintainPage } from './purchaseorder-maintain.page';
import { BarcodeScanner } from '@ionic-native/barcode-scanner/ngx';
import { PurchaseRequestMaintainPageModule } from '../../purchase-request/purchase-request-maintain/purchase-request-maintain.module';
import { SharedPRModalModule } from 'src/app/_modals/shared-pr-modal/shared-pr-modal.module';
import { PrSelectPage } from '../../purchase-request/modals/pr-select/pr-select.page';
import { PrItemSelectPage } from '../../purchase-request/modals/pr-item-select/pr-item-select.page';
import { PrItemPage } from '../../purchase-request/modals/pr-item/pr-item.page';
const routes: Routes = [
{
path: '',component: PurchaseorderMaintainPage
}
];
@NgModule({
imports: [
CommonModule,FormsModule,ReactiveFormsModule,IonicModule,RouterModule.forChild(routes),SharedPRModalModule
],providers: [
BarcodeScanner
],declarations: [PurchaseorderMaintainPage],entryComponents: [PrSelectPage,PrItemSelectPage,PrItemPage],})
export class PurchaseorderMaintainPageModule {}