使用 Javascript Map 和 Reduce 操作对象数组

Question

我已经这样做了：

import React from 'react';
const Header =(props)=>{
  const courseRecord =   props.course.map(line => line)
  return(
    <>
      <h2> {courseRecord[0].name }</h2>  
      <h2> {courseRecord[1].name }</h2> 
    </>
  )
}

const Part =(props) =>{
  return(
        <>
         <p>{props.partName}  {props.noOfEx}</p> 
        </>
  )
}

const Content =(props) =>{
  return(
    <div>        
           {props.course
            .map(kourse =>  kourse['parts']
            .map(parti =><Part key={parti['id']} partName = {parti['name']}   noOfEx =  {parti['exercises']}/> )
          )}  
    </div>
  )
}


const Total =(props) =>{
  // const numbers = props.course.parts;
  const numbers = props.course.map(kourse => kourse['parts']);
 
  var exTotal = numbers.reduce((totalExercises,currentValue) =>{
    console.log("totalExercises " , totalExercises , " current value " ,currentValue, " Exercises ",  currentValue[0][1])
      return totalExercises * currentValue.exercises
  },0 );
  return(
        <>
           <p><b>Total of {exTotal} exercises</b></p>
        </>
  )}

  const Course = (props) =>{
    let records =props.course.length;
      return(
        <>
          <h1>Web Development Curriculumn</h1>
          <Header course={props.course}  />
           <Content course ={props.course}/>  
          <Total course ={props.course}/>   
        </>
      )
  }

const  App = () => {
  const course =[
    {
      id: 1,
      name:'Half Stack application development',
      parts: [
        {
          name: 'Fundamentals of React',
          exercises: 10,
          id: 1
        },
        {
          name: 'Using props to pass data',
          exercises: 7,
          id: 2
        },
        {
          name: 'State of a component',
          exercises: 14,
          id: 3
        },
        {
          name: 'Destructuring',
          exercises: 14,
          id: 4
        }

      ]
    },
    {
      name :'Node JS',
      id: 2,
      parts:[
        {
          name: 'Routing',
          exercises: 3,
          id: 1
        },
        {
          name: 'middlewares',
          exercises: 7,
          id: 2
        }
      ]
    }
  ]

  return <Course course={course} />
}

export default App;

我希望以这种方式输出格式：

Web Development curriculum

Half Stack Application Development

Fundamentals of React 10
Using props to pass Data 7
State of Component 14
Destructuring 14

Total of 45 exercises

Node Js
Routing 3
Middlewares 7

total of 10 exercises

我明白了：

Web Development Curriculumn

Half Stack application development

Node JS
Fundamentals of React 10

Using props to pass data 7

State of a component 14

Destructuring 14

Routing 3

middlewares 7

Total of NaN exercises

我该如何解决？

Answer 1

当你使用数组时，请使用复数，所以课程数组应该是courses而不是course，只是循环似乎不正确，除了你的代码看起来很好。请检查以下示例代码。

import React from 'react';
const Header = ({ course }) => {
  return (
    <>
      <h2> {course.name}</h2>
    </>
  );
};

const Part = (props) => {
  return (
    <>
      <p>
        {props.partName} {props.noOfEx}
      </p>
    </>
  );
};

const Content = ({ course }) => {
  return (
    <div>
      {course['parts'].map((parti) => (
        <Part
          key={parti['id']}
          partName={parti['name']}
          noOfEx={parti['exercises']}
        />
      ))}
    </div>
  );
};

const Total = ({ course }) => {
  // const numbers = props.course.parts;

  var exTotal = course['parts'].reduce((totalExercises, currentValue) => {
    console.log(
      'totalExercises ',
      totalExercises,
      ' current value ',
      currentValue,
      ' Exercises ',
      currentValue
    );
    totalExercises = totalExercises + currentValue.exercises;
    return totalExercises;
  }, 0);
  return (
    <>
      <p>
        <b>Total of {exTotal} exercises</b>
      </p>
    </>
  );
};

const Course = ({ courses }) => {
  return (
    <>
      <h1>Web Development Curriculumn</h1>
      {courses && courses.length
        ? courses.map((course, index) => (
            <div key={index}>
              <Header course={course} />
              <Content course={course} />
              <Total course={course} />
            </div>
          ))
        : null}
    </>
  );
};

const App = () => {
  const courses = [
    {
      id: 1,
      name: 'Half Stack application development',
      parts: [
        {
          name: 'Fundamentals of React',
          exercises: 10,
          id: 1,
        },
        {
          name: 'Using props to pass data',
          exercises: 7,
          id: 2,
        },
        {
          name: 'State of a component',
          exercises: 14,
          id: 3,
        },
        {
          name: 'Destructuring',
          exercises: 14,
          id: 4,
        },
      ],
    },
    {
      name: 'Node JS',
      id: 2,
      parts: [
        {
          name: 'Routing',
          exercises: 3,
          id: 1,
        },
        {
          name: 'middlewares',
          exercises: 7,
          id: 2,
        },
      ],
    },
  ];

  return <Course courses={courses} />;
};

export default App;

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