Angular，TypeError：无法读取未定义的属性'toLowerCase' [英] Angular, TypeError: Cannot read property 'toLowerCase' of undefined

问题描述

我试图按照链接制作自定义过滤器管道，但我得到的错误说 Angular，TypeError：无法读取undefined 的属性'toLowerCase'。我已经将管道导入到 app.module.ts 中，并在声明中声明了它。任何人都可以帮我解决这个错误？

 < form id =filter > < input type =textclass =form-controlname =term[（ngModel）] =termplaceholder =按名称过滤/>< / form>< tr * ngFor = 让productList | paginate：{itemsPerPage：1，currentPage：p} | filter：term> < TD> {{product.prdName}}< / TD> < TD> {{product.prdCat}}< / TD> < td> {{product.prdSup}}< / td>< / tr>  

任何{if（term === undefined）return prdName; return prdName.filter（function（Product）{return Product.name.toLowerCase（）。includes（term.toLowerCase（））;}）




解决方案

code> transform（items：any，term：any）：any {
if（term === undefined）return items;

return items.filter（function（Product）{
return Product.prdName.toLowerCase（）。includes（term.toLowerCase（））;
}）
}





i'm trying to make a custom filter pipe by following this link, but i got error that said Angular, TypeError: Cannot read property 'toLowerCase' of undefined. I already imported the pipe to app.module.ts and also declared it in declaration. Can anyone help me with this error?

<form id="filter">
  <input type="text" class="form-control" name="term" [(ngModel)]="term" placeholder="filter by name" />
</form>

<tr *ngFor="let product of productList | paginate: { itemsPerPage: 1, currentPage: p } | filter: term">
  <td>{{product.prdName}}</td>
  <td>{{product.prdCat}}</td>
  <td>{{product.prdSup}}</td>
</tr>

@Pipe({
  name: 'filter'
})


transform(prdName: any, term: any): any {
    if (term === undefined) return prdName;

    return prdName.filter(function(Product) {
      return Product.name.toLowerCase().includes(term.toLowerCase());
    })

解决方案

try like this :

transform(items: any, term: any): any {
    if (term === undefined) return items;

    return items.filter(function(Product) {
        return Product.prdName.toLowerCase().includes(term.toLowerCase());
    })
}

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