如何在reactjs中更新数组的状态
我有一系列按钮的可见性。我正在将这些按钮的状态保存到状态如何在reactjs中更新数组的状态,reactjs,Reactjs,我有一系列按钮的可见性。我正在将这些按钮的状态保存到状态 this.state = { score: 0, status: "", userSelected: "", computerSelected: "", visibility: [true, true, true] }; 我想按索引更新可见性数组的值。我试着像下面这样做,但它并没有更新,它一直在数组中添加新元素,而不是更新数组的值 var arrayvar = this.state.visibility.slice(
this.state = {
score: 0,
status: "",
userSelected: "",
computerSelected: "",
visibility: [true, true, true]
};
我想按索引更新可见性数组的值。我试着像下面这样做,但它并没有更新,它一直在数组中添加新元素,而不是更新数组的值
var arrayvar = this.state.visibility.slice();
if (
(user === "Rock" && computer === "Paper") ||
(user === "Paper" && computer === "Rock")
) {
arrayvar.push(true, true, false); // here set 1st and 2nd to true and 3rd to false
} else if (
(user === "Rock" && computer === "Scissors") ||
(user === "Scissors" || computer === "Rock")
) {
arrayvar.push(true, false, true);
} else if (
(user === "Paper" && computer === "Scissors") ||
(user === "Scissors" || computer === "Paper")
) {
arrayvar.push(false, true, true);
} else if (user === "Rock" && computer === "Rock") {
arrayvar.push(true, false, false);
} else if (user === "Paper" && computer === "Paper") {
arrayvar.push(false, true, false);
} else if (user === "Scissors" && computer === "Scissors") {
arrayvar.push(false, false, true);
}
this.setState({ visibility: arrayvar });
任何人都可以在reactjs
中建议如何执行此操作吗?将始终在数组中推送新值,而不会更新现有值
你需要这样写:
arrayvar = []; //create a variable, don't need to copy the state values here
arrayvar = [true, true, false]; // assign new array inside conditions
this.setState({
visibility: arrayvar //then update the state visibility array
})
您不需要创建状态数组的副本
,因为您正在更新整个数组
而不是数组
的特定值,只需创建一个变量:
arrayvar = [];
完整代码:
var arrayvar = [];
if ( (user === "Rock" && computer === "Paper") || (user === "Paper" && computer === "Rock")) {
arrayvar = [true, true, false];
} else if ((user === "Rock" && computer === "Scissors") || (user === "Scissors" || computer === "Rock")) {
arrayvar = [true, false, true]
} else if ((user === "Paper" && computer === "Scissors") || (user === "Scissors" || computer === "Paper")) {
arrayvar = [false, true, true];
} else if (user === "Rock" && computer === "Rock") {
arrayvar = [true, false, false];
} else if (user === "Paper" && computer === "Paper") {
arrayvar = [false, true, false];
} else if (user === "Scissors" && computer === "Scissors") {
arrayvar = [false, false, true];
}
this.setState({ visibility: arrayvar });
将始终在数组中推送新值,但不会更新现有值
你需要这样写:
arrayvar = []; //create a variable, don't need to copy the state values here
arrayvar = [true, true, false]; // assign new array inside conditions
this.setState({
visibility: arrayvar //then update the state visibility array
})
您不需要创建状态数组的副本
,因为您正在更新整个数组
而不是数组
的特定值,只需创建一个变量:
arrayvar = [];
完整代码:
var arrayvar = [];
if ( (user === "Rock" && computer === "Paper") || (user === "Paper" && computer === "Rock")) {
arrayvar = [true, true, false];
} else if ((user === "Rock" && computer === "Scissors") || (user === "Scissors" || computer === "Rock")) {
arrayvar = [true, false, true]
} else if ((user === "Paper" && computer === "Scissors") || (user === "Scissors" || computer === "Paper")) {
arrayvar = [false, true, true];
} else if (user === "Rock" && computer === "Rock") {
arrayvar = [true, false, false];
} else if (user === "Paper" && computer === "Paper") {
arrayvar = [false, true, false];
} else if (user === "Scissors" && computer === "Scissors") {
arrayvar = [false, false, true];
}
this.setState({ visibility: arrayvar });
顺便说一下
var arrayvar = ["Rock", "Paper", "Scissors"]
.map(
k => computer === k || user === k
);
如果你写的话,很可能会取代整个
var arrayvar = ["Rock", "Paper", "Scissors"]
.map(
k => computer === k || user === k
);
如果你这样写的话,很可能会取代整体。但这就是它的作用。@OliverCharlesworth我明白了。“你知道怎么更新它吗?但这就是我所知道的。”奥利弗·卡莱斯沃思说。你知道更新它的方法吗?如果我没有更新完整的可见性数组,那么我需要克隆吗,然后怎么做?在这种情况下,首先创建一个副本,使用项索引更新特定值,然后更新状态,如下所示:let visibility=this.state.visibility.slice();可见性[项目索引]=值;this.setState({visibility})
非常感谢Mayank+1:)如果我没有更新完整的可见性数组,那么我需要克隆吗,然后怎么做?在这种情况下,首先创建一个副本,使用项索引更新特定值,然后更新状态,如下所示:让visibility=this.state.visibility.slice();可见性[项目索引]=值;this.setState({visibility})
非常感谢Mayank+1:)它将如何工作?你能解释一下吗。看起来是最佳方法+1它将数组中的每个“键”映射到“是计算机还是用户选择的”。它将如何工作?你能解释一下吗。看起来是最佳方法+1它将数组中的每个“键”映射到“无论是计算机还是用户选择的”。