如何计算数组中重复名称的出现次数-JavaScript？
假设以下是我们的数组-
var details = [
{
studentName: "John",
studentAge: 23
},
{
studentName: "David",
studentAge: 24
},
{
studentName: "John",
studentAge: 21
},
{
studentName: "John",
studentAge: 25
},
{
studentName: "Bob",
studentAge: 22
},
{
studentName: "David",
studentAge: 20
}
]我们需要计算重复名称的出现次数，即输出应为
John: 3 David: 2 Bob: 1
为此，您可以使用的概念reduce()。
示例
以下是代码-
var details = [
{
studentName: "John",
studentAge: 23
},
{
studentName: "David",
studentAge: 24
},
{
studentName: "John",
studentAge: 21
},
{
studentName: "John",
studentAge: 25
},
{
studentName: "Bob",
studentAge: 22
},
{
studentName: "David",
studentAge: 20
}
]
var output = Object.values(details.reduce((obj, { studentName }) => {
if (obj[studentName] === undefined)
obj[studentName] = { studentName: studentName, occurrences: 1 };
else
obj[studentName].occurrences++;
return obj;
}, {}));
console.log(output);要运行以上程序，您需要使用以下命令-
node fileName.js.
在这里，我的文件名为demo282.js。这将在控制台上产生以下输出-
PS C:\Users\Amit\javascript-code> node demo282.js
[
{ studentName: 'John', occurrences: 3 },
{ studentName: 'David', occurrences: 2 },
{ studentName: 'Bob', occurrences: 1 }
]