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呈現頁面時出現此錯誤

JavaScript

至尊寶的傳說 2023-02-24 16:09:31

我不明白這個錯誤。這是語法錯誤嗎？發生這種情況是因為 react-dom 版本嗎？在此塊上拋出錯誤。getWitnessName = (witnessId) => { if (this.props.witnesses) { return this.props.witnesses.find(el => el.account_id === witnessId).account_name; }}錯誤是：Uncaught TypeError: Cannot read property 'account_name' of undefinedat BlockList.__getWitnessName__REACT_HOT_LOADER__ (BlockList.js:212)at BlockList._this.getWitnessName (BlockList.js:76)at eval (BlockList.js:321)at Array.map (<anonymous>)at BlockList.render (BlockList.js:314)at finishClassComponent (react-dom.development.js:17160)at updateClassComponent (react-dom.development.js:17110)at beginWork (react-dom.development.js:18620)at HTMLUnknownElement.callCallback (react-dom.development.js:188)at Object.invokeGuardedCallbackDev (react-dom.development.js:237)The above error occurred in the <BlockList> component:in BlockList (created by Connect(BlockList))in Connect(BlockList) (created by Route)in Routein Switchin divin Router (created by ConnectedRouter)in ConnectedRouterin Providerin AppContainer

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4 回答

慕雪6442864

TA貢獻1812條經驗獲得超5個贊

如果你看到下面的代碼，如果它沒有找到與給定的 witnessId 匹配的任何 account_id，則 witness var 可以是未定義的。在這種情況下，會拋出錯誤，所以這樣做

getWitnessName = (witnessId) => {

if (this.props.witnesses) {

const witness = this.props.witnesses.find(el => el.account_id === witnessId)

return witness ? witness.account_name : `No witness for given id: ${witnessId}`;

}

反對回復 2023-02-24

catspeake

TA貢獻1111條經驗獲得超0個贊

您可以使用可選鏈接

添加一個nullish 合并運算符來完成圖片而不是正常的，||它不會對虛假值做出反應

return this.props.witnesses.find(el => el.account_id === witnessId)?.account_name ?? "N/A";

它將處理丟失的 witness 和丟失的 account_name

例子

const props = {

witnesses: [

{ account_id: 1, account_name: "Fred"},

{ account_id: 2, account_name: "Joe" },

{ account_id: 3 }]

};

const getName = witnessId => props.witnesses

.find(el => el.account_id === witnessId)?.account_name ?? "N/A";

console.log(getName(1))

console.log(getName(2))

console.log(getName(3))

console.log(getName(4))

反對回復 2023-02-24

慕標琳琳

TA貢獻1830條經驗獲得超9個贊

嘗試首先驗證以獲取屬性，這是因為它沒有找到任何驗證輸入。然后 find 返回 undefined，你不能從 undefined 中獲取屬性。

例如

this.props.witnesses.find(el => el.account_id === witnessId)?.account_name ?? 'Account Not Found';

反對回復 2023-02-24

慕桂英546537

TA貢獻1848條經驗獲得超10個贊

getWitnessName = (witnessId) => {

if (this.props.witnesses) {

let foundWitnesses = this.props.witnesses.find(el => el.account_id === witnessId);

if(foundWitnesses)

return foundWitnesses.account_name;

else

return 'Not found';

}

反對回復 2023-02-24

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呈現頁面時出現此錯誤

呈現頁面時出現此錯誤

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