如何从数组中编写随机按钮？

Question

我需要创建一个多项选择题，其中正确答案显示在四个按钮之一上（我不知道哪一个，因为这将随机生成）。然后用户必须通过按下按钮选择正确的答案。

我的问题是：我如何编写“If”语句，当按下按钮时，当我不知道哪个按钮是正确的时？

这是代码

Answer 1

试试这个：

import { Component, Input, OnInit } from '@angular/core';
import { MyData} from './mydata';
import { ActivatedRoute } from '@angular/router';
import { OtherService } from './other.service';
import { Observable } from 'rxjs/Observable';
import { Subject } from 'rxjs/Subject';
import { Headers, RequestOptions } from '@angular/http';
import { ParameterService } from '../parameter.service';
import { LocalStorageService } from 'angular-2-local-storage';

@Component({
    templateUrl: 'app/test/test.component.html'
})

export class TestComponent implements OnInit {

    subscription: any;
    customerId: string;

    // set getter as a property on the variable `year`:
    ////year: string;
    get year(): string {
      console.log("test.component.get()");
      const value = this._parameterService.p['year'] + "";
      // Any other code you need to execute when the data is changed here
      this.getDataFromApi();
      return value;
    }

    private sub: any;

    errorMessage: string;
    data: MyData[];
    constructor(private _otherService: OtherService,
        private _parameterService: ParameterService,
        private _route: ActivatedRoute,
        private _localStorageService: LocalStorageService) { }

    getDataFromApi() {

        // store route parameters in Local Storage
        // if none found, try reading from Local Storage
        if (this.customerId == null)
            this.customerId = this._localStorageService.get('customerId') + "";
        //if (this.year== null)
        //    this.year = this._localStorageService.get('year') + "";            

        this._localStorageService.set('customerId', this.customerId);
        //this._localStorageService.set('year', this.year);

        // try getting YEAR (not customerId, yet) from getter
        this._otherService.getDataFromApi(this.customerId, this.year)
            .then(
            data => this.data = data,
            error => this.errorMessage = <any>error);
    }

    getData(): void{
        this.data = this._otherService.getData();
    }

    resetComponentState(): void {
        this.getDataFromApi();
    }

    ngOnInit(): void {

        this.sub = this._route.params.subscribe(params => {
            this.customerId = params['customerId'];
            //this.year = params['year'];

            this.resetComponentState(); // based on new parameter this time
        });
    }
}