正在处理HTML / JS Mediator,当用户在字段中输入文本时,它会过滤data_model。使用了window.onload = init,并花了四个小时试图找到浏览器中的'this'为什么打印调用对象,因此我无法使用'this'来获取类实例来引用自己
console.log(this.text_field)
setup_list_view()中的工作正常,貌似因为它在构造函数范围内。在构造函数外部运行它,如下所示,给出:
Cannot set property 'innerHTML' of undefined at HTMLInputElement.handle_text_field_changed
...
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<script>
function init() {
var text_field = document.getElementById("text-field");
var list_view = document.getElementById("list-view")
form_mediator = new FormMediator(text_field, list_view)
}
class FormMediator {
constructor(text_field, list_view) {
this.setup_text_field(text_field)
this.setup_list_view(list_view)
}
setup_text_field(text_field) {
this.text_field = text_field;
this.text_field.onchange = this.handle_text_field_changed
}
setup_list_view(list_view) {
this.data_model = ['England', 'Estonia', 'France', 'Germany']
this.list_view = list_view
this.list_view.innerHTML = this.data_model
}
does_string_start_with_text_field_text(text) {
return false;
return text.startsWith('E')
}
handle_text_field_changed(){
this.list_view.innerHTML = 'new content' //this.data_model.filter(this.does_string_start_with_text_field_text)
}
}
window.onload = init
</script>
<input id="text-field"><button>Search</button>
<span id="list-view"></span>
</body>
</html>
任何帮助都非常感激。
答案 0 :(得分:1)
代码中出现问题:
this.text_field.onchange = this.handle_text_field_changed
默认情况下,如果将方法分配给变量或其他对象的属性,则该方法不会携带其原始绑定上下文。您需要首先以这种方式绑定此handle_text_field_changed方法:
this.text_field.onchange = this.handle_text_field_changed.bind(this)