javascript - default content disappears when adding formControlName the <textarea> element</h1> <div id="body"><p>I'm trying to create a Reactive Form in Angular 4.0.2, which has a <code><textarea></code> field with</a></h1> <div class="ml12 aside-cta flex--item print:d-none sm:ml0 sm:mb12 sm:order-first sm:as-end"> <a href="https://stackoverflow.com/questions/ask" target="_blank" class="ws-nowrap s-btn s-btnprimary">问问题</a></div> </div> <div class="d-flex fw-wrap pb8 mb16 bb bc-black-075"> <div class="flex--item ws-nowrap mr16 mb8"> <span class="fc-light mr2"></span> </div> <div class="flex--item ws-nowrap mr16 mb8" title="2022-04-17 15:46:40Z"> <span class="fc-light mr2">问问题</span> <time itemprop="dateCreated" datetime="2017-04-29T18:10:04.590">2017-04-29T18:10:04.590</time> </div> <div class="flex--item ws-nowrap mb8" title="Viewed 6 times"> <span class="fc-light mr2"></span> 10082 次 </div> </div> <div id="mainbar" role="main" aria-label="question and answers"> <div class="question" 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</div> </div> </div> <a name="7"></a> <div id="answer-7" class="answer js-answer accepted-answer" data-answerid="7" data-parentid="4" data-score="506" data-position-on-page="1" data-highest-scored="1" data-question-has-accepted-highest-score="1" itemprop="suggestedAnswer" itemscope="" itemtype="https://schema.org/Answer"> <div class="post-layout"> <div class="votecell post-layout--left"> <div class="js-voting-container d-flex jc-center fd-column ai-stretch gs4 fc-black-200" data-post-id="7"> <button class="js-vote-up-btn flex--item s-btn s-btnunset c-pointer " data-controller="s-tooltip" data-s-tooltip-placement="right" aria-pressed="false" aria-label="Up vote" data-selected-classes="fc-theme-primary" data-unselected-classes="" aria-describedby="--stacks-s-tooltip-dgvag2l3"> <svg aria-hidden="true" class="svg-icon iconArrowUpLg" width="36" height="36" viewBox="0 0 36 36"><path d="M2 25h32L18 9 2 25Z"></path></svg> </button><div id="--stacks-s-tooltip-dgvag2l3" class="s-popover s-popovertooltip pe-none" aria-hidden="true" role="tooltip">This answer is useful<div class="s-popover--arrow"></div></div> <div class="js-vote-count flex--item d-flex fd-column ai-center fc-black-500 fs-title" itemprop="upvoteCount" data-value="7"> 7 </div> <button class="js-vote-down-btn flex--item s-btn s-btnunset c-pointer " data-controller="s-tooltip" data-s-tooltip-placement="right" aria-pressed="false" aria-label="Down vote" data-selected-classes="fc-theme-primary" data-unselected-classes="" aria-describedby="--stacks-s-tooltip-gn8ppsfv"> <svg aria-hidden="true" class="svg-icon iconArrowDownLg" width="36" height="36" viewBox="0 0 36 36"><path d="M2 11h32L18 27 2 11Z"></path></svg> </button> </div> </div> <div class="answercell post-layout--right"> <div class="s-prose js-post-body" itemprop="text"> <p>改用默认值</p> <pre><code>this.sectionForm = new FormGroup({ sectionTitle: new FormControl(), sectionContent : new FormControl(this.section.sectionContent) }); </code></pre> <p>模板</p> <pre><code><textarea formControlName="sectionContent"></textarea> </code></pre> <p>或使用 setValue/pathValue：</p> <pre><code>this.sectionForm = new FormGroup({ sectionTitle: new FormControl(), sectionContent : new FormControl() }); // after received data this.sectionForm.patchValue({sectionContent: this.section.sectionContent}); </code></pre> <p>演示：<a href="https://plnkr.co/edit/NWgzGdUc9cDkKujPgrl4?p=preview" rel="noreferrer">https ://plnkr.co/edit/NWgzGdUc9cDkKujPgrl4?p=preview</a></p> <p>文档：</p> <p><a href="https://angular.io/docs/ts/latest/api/forms/index/FormControl-class.html" rel="noreferrer">https://angular.io/docs/ts/latest/api/forms/index/FormControl-class.html </a> <a href="https://angular.io/docs/ts/latest/api/forms/index/FormGroup-class.html" rel="noreferrer">https://angular.io/docs/ts/latest/api/forms/index/FormGroup-class.html</a></p> <p>设定值：</p> <blockquote> <p>设置 FormGroup 的值。它接受与组结构匹配的对象，以控件名称作为键。</p> <p>此方法执行严格检查，因此如果您尝试设置不存在的控件的值或排除控件的值，它将引发错误。</p> </blockquote> <p>补丁值：</p> <blockquote> <p>修补 FormGroup 的值。它接受一个以控件名称作为键的对象，并尽最大努力将值与组中的正确控件相匹配。</p> <p>它接受组的超集和子集而不会引发错误。</p> </blockquote> </div> <div class="mt24"> <div class="user-action-time" style="color:#999;text-align:right;">于 2017-04-29T18:15:43.823 回答</div> </div> </div> </div> </div></div> </div> <div id="sidebar" class="show-votes" role="complementary" aria-label="sidebar"> <div class="module sidebar-related"> <h4 id="h-related">Related</h4> <div class="related js-gps-related-questions" data-tracker="rq=1"> <div class="spacer"> <a href="/questions/10628149" title="Question score (upvotes - downvotes)"> <div class="answer-votes large">6</div> </a> <a href="/questions/10628149" class="question-hyperlink">heroku - 更改密码后无法使用heroku gem cli</a> </div><div class="spacer"> <a href="/questions/10628152" title="Question score (upvotes - downvotes)"> <div class="answer-votes large">5</div> </a> <a href="/questions/10628152" class="question-hyperlink">android - 动态获取活动名称 - android</a> </div><div 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