问题描述
我以前在Angular 4应用程序中使用过lodash，只需将其导入并按如下所示使用它:
I have previously used lodash in my Angular 4 application by simply importing it and using it as shown here:
import lodash from 'lodash';
public getSubtotal() : number {
return lodash.sumBy(this.cartItems, function(item) {
return item.product.price * item.item.quantity;
})
}
我再次尝试类似地使用lodash，但是却收到一个错误，表明lodash是未定义的.
I am once again trying to use lodash similarly but am getting an error that lodash is undefined.
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)
推荐答案
首先，您需要安装软件包 lodash 和 @ types/lodash (包含类型定义):
First you need to install the packages lodash and @types/lodash (contains type definitions):
npm i lodash
npm i --save-dev @types/lodash
然后您可以使用lodash例如与import * as _ from 'lodash';并进一步执行_.indexOf([1, 2, 1, 2], 2);
Then you can use lodash e.g. with import * as _ from 'lodash'; and further do _.indexOf([1, 2, 1, 2], 2);
您也可以执行import * as _isEmpty from 'lodash/isEmpty';(感谢joshrathke)或import {isEmpty} from 'lodash';
You could also do import * as _isEmpty from 'lodash/isEmpty'; (thanks to joshrathke) or import {isEmpty} from 'lodash';
这篇关于在Angular 4中使用lodash的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！