javascript - push 方法不返回新数组

Question

我正在通过 javascript push() 方法将对象添加到数组。我的数组是一个对象数组。我想 console.log() 新数组。但它给了我新数组的长度。我知道 push() 方法返回新数组的长度，但我想在我的应用程序中使用新数组。获取方式

    let sub_sprite = this.state.sub_sprite;
    let updated_sub_subsprite;
    updated_sub_subsprite = sub_sprite.push(this.state.sprite[that.state.sprite_count]);
    console.log(updated_sub_subsprite);

    that.setState({sub_sprite:updated_sub_subsprite}, ()=>{
         console.log(this.state.sub_sprite)
    });

Answer 1

不要使用 Array.push在存储在 React 组件状态中的数组上，它会直接改变状态，这可能会导致问题(see this article)。

您可以使用 Array.concat使用附加值创建一个新数组:

let sub_sprite = this.state.sub_sprite
let updated_sub_subsprite;
updated_sub_subsprite = sub_sprite.concat([this.state.sprite[that.state.sprite_count]]);
console.log(updated_sub_subsprite);
that.setState({sub_sprite:updated_sub_subsprite}, ()=> {
    console.log(this.state.sub_sprite)
})

更简洁方便的方法是使用 spread syntax (注意三个点):

let sub_sprite = this.state.sub_sprite
let updated_sub_subsprite;
updated_sub_subsprite = [...sub_sprite, this.state.sprite[that.state.sprite_count]);
console.log(updated_sub_subsprite);
that.setState({sub_sprite:updated_sub_subsprite}, ()=> {
    console.log(this.state.sub_sprite)
})