Object.keys-需要一个赋值或函数调用,而是看到一个表达式no-unused-expressions

时间:2019-07-14 17:04:47

标签: javascript reactjs

在ReactJS中使用多个javascript方法创建html表。 Object.keys用于从对象中提取数据。在呈现主题,主体,tr和td而不显示消息时出现问题,“预期分配或函数调用,而是看到了表达式no-unused-expressions”。

import React from 'react';

const CreateTable = ({ results }) => {

    //headers should be based on keys
    const CreateHeaders = () => {
        return (
            <thead>
                <tr>
                    {Object.keys(results.header).forEach(function(column){
                        // console.log(column);
                        <td>
                            {column}
                        </td>
                    })}
                </tr>
            </thead>
        )
    }

    const CreateBody = ( ) => {
        return (
            <tbody>
                {Object.keys(results.data).forEach(function(tr){
                    // console.log(results.data[tr])
                   <tr>
                       {CreateRows(results.data[tr])}
                  </tr> 
                })}
            </tbody>
        )
    }

    const CreateRows = (tr) => {
        return(
        Object.keys(tr).forEach(function(td){
            console.log(tr[td]);
            <td>{tr[td]}</td>
        }));
    }

    if( results.data !== null && results.data !== undefined){
        console.log(<table>{CreateHeaders()}{CreateBody()}</table>);
        return <table>{CreateHeaders()}{CreateBody()}</table>
    }
    else {
        return (null);
    }


}

export { CreateTable }

我希望有一个表可以渲染,但是我收到一条消息,提示,

第12行:预期分配或函数调用,而是看到一个表达式no-unused-expressions   第26行:预期分配或函数调用,而是看到一个表达式no-unused-expressions   第38行:需要执行赋值或函数调用,而是看到了表达式no-unused-expressions

我可以在object.keys函数内部设置一个返回值,但是当我什么都不做时,除了表的骨架之外,什么都不呈现。 IE浏览器

<table><thead></thead><tbody></tbody></table>

从if语句到上面显示的代码底部的Console.log输出

{$$typeof: Symbol(react.element), type: "table", key: null, ref: null, props: {…}, …}
$$typeof: Symbol(react.element)
key: null
props:
children: Array(2)
0:
$$typeof: Symbol(react.element)
key: null
props:
children:
$$typeof: Symbol(react.element)
key: null
props: {children: undefined}
ref: null
type: "tr"
_owner: FiberNode {tag: 0, key: null, elementType: ƒ, type: ƒ, stateNode: null, …}
_store: {validated: true}
_self: null
_source: {fileName: "...\src\components\table.js", lineNumber: 10}
__proto__: Object
__proto__: Object
ref: null
type: "thead"
_owner: FiberNode {tag: 0, key: null, elementType: ƒ, type: ƒ, stateNode: null, …}
_store: {validated: true}
_self: null
_source: {fileName: "...\src\components\table.js", lineNumber: 9}
__proto__: Object
1:
$$typeof: Symbol(react.element)
key: null
props: {children: undefined}
ref: null
type: "tbody"
_owner: FiberNode {tag: 0, key: null, elementType: ƒ, type: ƒ, stateNode: null, …}
_store: {validated: true}
_self: null
_source: {fileName: "...\src\components\table.js", lineNumber: 24}
__proto__: Object
length: 2
__proto__: Array(0)
__proto__: Object
ref: null
type: "table"

1 个答案:

答案 0 :(得分:4)

您正在使用没有返回值的forEach。您正在寻找map

<tr>
    {Object.keys(results.header).map(column => (
        // console.log(column);
        <td>
            {column}
        </td>
    ))}
</tr>

然后从CreateRows

返回地图的结果
const CreateRows = (tr) => {
    return(
    Object.keys(tr).map(td =>
        <td>{tr[td]}</td>
    ));
}