类型“Element”上不存在属性“style”

因为ts默认用的是Element，需要声明为HTMLElement

let top = <HTMLImageElement>document.querySelector('.Top');
top.style.display = 'none' ;

或是下面这样 

let top = document.querySelector('.Top') as HTMLElement;
top.style.display = 'none' ;

当然如果你用的是angular的话，建议用 ElementRef

import { Component, ElementRef } from '@angular/core';

constructor(
        private elementRef: ElementRef
) {

}
this.elementRef.nativeElement.querySelector('#select_id');