angular - 在 Angular 4 中使用 lodash

Question

我以前在我的 Angular 4 应用程序中使用过 lodash，方法是简单地导入它并使用它，如下所示:

import lodash from 'lodash';

public getSubtotal() : number {
  return lodash.sumBy(this.cartItems, function(item) {        
    return item.product.price * item.item.quantity;
  })

我再次尝试以类似方式使用 lodash，但收到 lodash 未定义的错误。

import lodash from 'lodash';

lodash.indexOf([1, 2, 1, 2], 2);

我收到以下错误:

ERROR TypeError: Cannot read property 'indexOf' of undefined
at CustomizeComponent.showTopping (customize.component.ts:39)
at Object.eval [as updateDirectives] (CustomizeComponent.html:285)
at Object.debugUpdateDirectives [as updateDirectives] (core.js:14638)
at checkAndUpdateView (core.js:13785)
at callViewAction (core.js:14136)
at execComponentViewsAction (core.js:14068)
at checkAndUpdateView (core.js:13791)
at callViewAction (core.js:14136)
at execEmbeddedViewsAction (core.js:14094)
at checkAndUpdateView (core.js:13786)

Answer 1

首先你需要安装软件包lodash和 @types/lodash (包含类型定义):

npm i lodash
npm i --save-dev @types/lodash

然后你可以使用 lodash 例如使用 import * as _ from 'lodash'; 并进一步执行 _.indexOf([1, 2, 1, 2], 2];

您还可以import * as _isEmpty from 'lodash/isEmpty';(感谢 joshrathke)或import {isEmpty} from 'lodash';