public webdesign: Array<WebDesign>;

loadMore() : void
{
    this.apollo.query(`{
          getWebDesignList (page : ${this.page++}) {
            _id
            title
            description
            creatorName
            createdAt
          }
     }`).subscribe(r => {
        r.data.getWebDesignList.forEach(e => this.webdesign.push(e));
        //TypeError: Cannot add property 2, object is not extensible
    });
}

let temp = JSON.parse(JSON.stringify(this.webdesign));
for (let i = 0; i < r.data.getWebDesignList.length; i++) {
    temp.push(r.data.getWebDesignList[i]);
}
this.webdesign = temp;