findIndex() 总是在带有对象的数组上返回-1

Question

我没有找到以下问题的解决方案。在这种情况下，索引一直返回 -1 而不是 1。任何人都可以帮助我吗？let allRules = [{ruleName: "a"}, {ruleName: "b"}, {ruleName: "c"}]let name = "b"let index = allRules.findIndex(x => {  console.log(x.ruleName)  x.ruleName === name})console.log(index)

Answer 1

您需要在回调方法中使用return关键字{}：

let allRules = [{ruleName: "a"}, {ruleName: "b"}, {ruleName: "c"}]

let name = "b"

let index = allRules.findIndex(x => {

  console.log(x.ruleName)

  return x.ruleName == name

})

console.log(index)

一个没有return声明的例子：

let allRules = [{ruleName: "a"}, {ruleName: "b"}, {ruleName: "c"}]

let name = "b"

let index = allRules.findIndex(x => x.ruleName == name)

console.log(index)

Answer 2

您需要添加退货。

let allRules = [{ruleName: "a"}, {ruleName: "b"}, {ruleName: "c"}]

let name = "b"

let index = allRules.findIndex(x => {

  console.log(x.ruleName)

  return x.ruleName === name

})

console.log(index)

Answer 3

正如@Nick Parsons 在评论中所说，你需要return一些东西。

let allRules = [{ruleName: "a"}, {ruleName: "b"}, {ruleName: "c"}]

let name = "b"

let index = allRules.findIndex(x => {

  console.log(x.ruleName);

  return x.ruleName === name;

})

console.log(index)