刚刚尝试了@蒂莫西佩雷斯的回答，并添加了一行

if (value.length < limit)
   return `${value.substr(0, limit)}`;

to

import { Pipe, PipeTransform } from '@angular/core';

@Pipe({
  name: 'truncate'
})
export class TruncatePipe implements PipeTransform {
transform(value: string, limit = 25, completeWords = false, ellipsis = '...') {

   if (value.length < limit)
   return `${value.substr(0, limit)}`;

   if (completeWords) {
     limit = value.substr(0, limit).lastIndexOf(' ');
   }
   return `${value.substr(0, limit)}${ellipsis}`;
}
}

根据单词限制长度

如果您想根据单词而不是字符进行截断，同时还允许一个选项查看完整的文本，可以试试这个方法。

来到这里寻找一个阅读更多的解决方案基于文字，分享自定义管道我最终写。

管:

import { Pipe, PipeTransform } from '@angular/core';

@Pipe({
  name: 'readMore'
})
export class ReadMorePipe implements PipeTransform {

  transform(text: any, length: number = 20, showAll: boolean = false, suffix: string = '...'): any {
    
    if (showAll) {
      return text;
    }

    if ( text.split(" ").length > length ) {
      
      return text.split(" ").splice(0, length).join(" ") + suffix;
    }

    return text;
  }

}

在模板:

<p [innerHTML]="description | readMore:30:showAll"></p>
<button (click)="triggerReadMore()" *ngIf="!showAll">Read More<button>

组件:

export class ExamplePage implements OnInit {

    public showAll: any = false;
    
    triggerReadMore() {
        this.showAll = true;
    }
    
}

在模块:

import { ReadMorePipe } from '../_helpers/read-more.pipe';

@NgModule({
  declarations: [ReadMorePipe]
})
export class ExamplePageModule {}

使用slice pipe (angular的核心管道)非常简单，就像你要求data.title一样:

{{ data.title | slice:0:20 }}

来自Angular通用文档https://angular.io/api/common/SlicePipe

两种方法将文本截断成角。

let str = 'How to truncate text in angular';

1. 解决方案

  {{str | slice:0:6}}

输出:

   how to

如果你想在切片字符串之后追加任何文本，比如

   {{ (str.length>6)? (str | slice:0:6)+'...':(str) }}

输出:

 how to...

2. 解决方案(创建自定义管道)

如果要创建自定义截断管道

import { Pipe, PipeTransform } from '@angular/core';

@Pipe({
 name: 'truncate'
})

export class TruncatePipe implements PipeTransform {

transform(value: string, args: any[]): string {
    const limit = args.length > 0 ? parseInt(args[0], 10) : 20;
    const trail = args.length > 1 ? args[1] : '...';
    return value.length > limit ? value.substring(0, limit) + trail : value;
   }
}

在标记

{{ str | truncate:[20] }} // or 
{{ str | truncate:[20, '...'] }} // or

不要忘记添加一个模块条目。

@NgModule({
  declarations: [
    TruncatePipe
  ]
})
export class AppModule {}

用可选参数截断管道:

Limit - string最大长度 completeWords -标记在最近的完整单词处截断，而不是字符 省略号——附加在后面的后缀

-

import { Pipe, PipeTransform } from '@angular/core';

@Pipe({
  name: 'truncate'
})
export class TruncatePipe implements PipeTransform {
  transform(value: string, limit = 25, completeWords = false, ellipsis = '...') {
    if (completeWords) {
      limit = value.substr(0, limit).lastIndexOf(' ');
    }
    return value.length > limit ? value.substr(0, limit) + ellipsis : value;
  }
}

不要忘记添加一个模块条目。

@NgModule({
  declarations: [
    TruncatePipe
  ]
})
export class AppModule {}

使用

示例字符串:

public longStr = 'A really long string that needs to be truncated';

标记:

  <h1>{{longStr | truncate }}</h1> 
  <!-- Outputs: A really long string that... -->

  <h1>{{longStr | truncate : 12 }}</h1> 
  <!-- Outputs: A really lon... -->

  <h1>{{longStr | truncate : 12 : true }}</h1> 
  <!-- Outputs: A really... -->

  <h1>{{longStr | truncate : 12 : false : '***' }}</h1> 
  <!-- Outputs: A really lon*** -->

如果你想要截断一些单词并添加一个省略号，你可以使用这个函数:

truncate(value: string, limit: number = 40, trail: String = '…'): string {
  let result = value || '';

  if (value) {
    const words = value.split(/\s+/);
    if (words.length > Math.abs(limit)) {
      if (limit < 0) {
        limit *= -1;
        result = trail + words.slice(words.length - limit, words.length).join(' ');
      } else {
        result = words.slice(0, limit).join(' ') + trail;
      }
    }
  }

  return result;
}

例子:

truncate('Bacon ipsum dolor amet sirloin tri-tip swine', 5, '…')
> "Bacon ipsum dolor amet sirloin…"

来自: https://github.com/yellowspot/ng2-truncate/blob/master/src/truncate-words.pipe.ts

如果你想要截断一些字母，但不删减单词，请使用以下命令:

truncate(value: string, limit = 25, completeWords = true, ellipsis = '…') {
  let lastindex = limit;
  if (completeWords) {
    lastindex = value.substr(0, limit).lastIndexOf(' ');
  }
  return `${value.substr(0, limit)}${ellipsis}`;
}

例子:

truncate('Bacon ipsum dolor amet sirloin tri-tip swine', 19, true, '…')
> "Bacon ipsum dolor…"

truncate('Bacon ipsum dolor amet sirloin tri-tip swine', 19, false, '…')
> "Bacon ipsum dolor a…"