这是因为switch语句是一个语句，但这里javascript需要一个表达式。

虽然，不建议在呈现方法中使用switch语句，但你可以使用自调用函数来实现这一点:

render() {
    // Don't forget to return a value in a switch statement
    return (
        <div>
            {(() => {
                switch(...) {}
            })()}
        </div>
    );
}

这个答案专门用来解决@tonyfat提出的“重复”问题，关于如何使用条件表达式来处理相同的任务。

---

Avoiding statements here seems like more trouble than it's worth, but this script does the job as the snippet demonstrates:

// Runs tests let id = 0, flag = 0; renderByFlag(id, flag); // jobId out of range id = 1; // jobId in range while(++flag < 5){ // active flag ranges from 1 to 4 renderByFlag(id, flag); } // Defines a function that chooses what to render based on two provided values function renderByFlag(jobId, activeFlag){ jobId === 1 ? ( activeFlag === 1 ? render("A (flag = 1)") : activeFlag === 2 ? render("B (flag = 2)") : activeFlag === 3 ? render("C (flag = 3)") : pass(`flag ${activeFlag} out of range`) ) : pass(`jobId ${jobId} out of range`) } // Defines logging functions for demo purposes function render(val){ console.log(`Rendering ${val}`); } function pass(reason){ console.log(`Doing nothing (${reason})`) }

我在render()方法中做了这个:

  render() {
    const project = () => {
      switch(this.projectName) {

        case "one":   return <ComponentA />;
        case "two":   return <ComponentB />;
        case "three": return <ComponentC />;
        case "four":  return <ComponentD />;

        default:      return <h1>No project match</h1>
      }
    }

    return (
      <div>{ project() }</div>
    )
  }

我试图保持render()返回干净，所以我把我的逻辑放在一个'const'函数上面。这样我也可以缩进我的开关盒整齐。

你可以这样做。

 <div>
          { object.map((item, index) => this.getComponent(item, index)) }
 </div>

getComponent(item, index) {
    switch (item.type) {
      case '1':
        return <Comp1/>
      case '2':
        return <Comp2/>
      case '3':
        return <Comp3 />
    }
  }

  const [route, setRoute] = useState(INITIAL_ROUTE)

  return (
    <RouteContext.Provider value={{ route, setRoute }}>
      {(() => {
        switch (route) {
          case Route.Home:
            return <PopupHomePage />
          case Route.App:
            return <PopupAppPage />
          default:
            return null
        }
      })()}
    </RouteContext.Provider>

这是另一种方法。

render() {
   return {this[`renderStep${this.state.step}`]()}

renderStep0() { return 'step 0' }
renderStep1() { return 'step 1' }