为啥在html页面中导入js不能用，在本页又行，，急。。。
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篇首语：本文由小常识网(cha138.com)小编为大家整理，主要介绍了为啥在html页面中导入js不能用，在本页又行，，急。。。相关的知识，希望对你有一定的参考价值。
参考技术A 原因很多，路径问题，head加载问题，或者必须完全加载后才能成功的问题请把你导入的内容发来追问 参考技术B 一般有2种情况 导入路径 导入方式 参考技术C 把你的导入路径写上来追问
但是我不加载，在本页又可以用，还没有遇见过这样的问题
你的html页底下是不是有一个js文件夹，该文件夹下有VarcharList.js，
是的话那在本页能够使用的地方插入，
而不是其他地方
为啥我不能在 react native 中导入我的自定义组件
【中文标题】为啥我不能在 react native 中导入我的自定义组件【英文标题】：why can't i import my custom component in react native为什么我不能在 react native 中导入我的自定义组件 【发布时间】：2021-06-07 08:54:11 【问题描述】：我创建了这些组件，我试图在 App.js 中导入它们，但它向我显示一条错误消息，我试图多次更改导出默认类，我改变了导入行的顺序以确定是否存在' e 导入其中一个组件时出错，但没有任何改变，仍然显示相同的错误消息，我该如何修复它
App.js
import React, Component from "react";
import ActivityIndicator,Keyboard,KeyboardAvoidingView,StyleSheet from "react-native";
import theme from './constants';
import Block from './app/components' ;
import Button from './app/components' ;
import Text from './app/components' ;
import Input from './app/components' ;
const VALID_EMAIL = "contact@react-ui-kit.com";
const VALID_PASSWORD = "subscribe";
export default class Login extends Component
state =
email: VALID_EMAIL,
password: VALID_PASSWORD,
errors: [],
loading: false
;
handleLogin()
const navigation = this.props;
const email, password = this.state;
const errors = [];
Keyboard.dismiss();
this.setState( loading: true );
// check with backend API or with some static data
if (email !== VALID_EMAIL)
errors.push("email");
if (password !== VALID_PASSWORD)
errors.push("password");
this.setState( errors, loading: false );
if (!errors.length)
navigation.navigate("Browse");
render()
const navigation = this.props;
const loading, errors = this.state;
const hasErrors = key => (errors.includes(key) ? styles.hasErrors : null);
return (
<KeyboardAvoidingView style=styles.login behavior="padding">
<Block padding=[0, theme.sizes.base * 2]>
<Text h1 bold>
Login
</Text>
<Block middle>
<Input
label="Email"
error=hasErrors("email")
style=[styles.input, hasErrors("email")]
defaultValue=this.state.email
onChangeText=text => this.setState( email: text )
/>
<Input
secure
label="Password"
error=hasErrors("password")
style=[styles.input, hasErrors("password")]
defaultValue=this.state.password
onChangeText=text => this.setState( password: text )
/>
<Button gradient onPress=() => this.handleLogin()>
loading ? (
<ActivityIndicator size="small" color="white" />
) : (
<Text bold white center>
Login
</Text>
)
</Button>
<Button onPress=() => navigation.navigate("Forgot")>
<Text
gray
caption
center
style= textDecorationLine: "underline"
>
Forgot your password?
</Text>
</Button>
</Block>
</Block>
</KeyboardAvoidingView>
);
const styles = StyleSheet.create(
login:
flex: 1,
justifyContent: "center"
,
input:
borderRadius: 0,
borderWidth: 0,
borderBottomColor: theme.colors.gray2,
borderBottomWidth: StyleSheet.hairlineWidth
,
hasErrors:
borderBottomColor: theme.colors.accent
);
Block.js
import React, Component from "react";
import StyleSheet, View, Animated from "react-native";
import theme from "./constants";
export default class Block extends Component
handleMargins()
const margin = this.props;
if (typeof margin === "number")
return
marginTop: margin,
marginRight: margin,
marginBottom: margin,
marginLeft: margin
;
if (typeof margin === "object")
const marginSize = Object.keys(margin).length;
switch (marginSize)
case 1:
return
marginTop: margin[0],
marginRight: margin[0],
marginBottom: margin[0],
marginLeft: margin[0]
;
case 2:
return
marginTop: margin[0],
marginRight: margin[1],
marginBottom: margin[0],
marginLeft: margin[1]
;
case 3:
return
marginTop: margin[0],
marginRight: margin[1],
marginBottom: margin[2],
marginLeft: margin[1]
;
default:
return
marginTop: margin[0],
marginRight: margin[1],
marginBottom: margin[2],
marginLeft: margin[3]
;
handlePaddings()
const padding = this.props;
if (typeof padding === "number")
return
paddingTop: padding,
paddingRight: padding,
paddingBottom: padding,
paddingLeft: padding
;
if (typeof padding === "object")
const paddingSize = Object.keys(padding).length;
switch (paddingSize)
case 1:
return
paddingTop: padding[0],
paddingRight: padding[0],
paddingBottom: padding[0],
paddingLeft: padding[0]
;
case 2:
return
paddingTop: padding[0],
paddingRight: padding[1],
paddingBottom: padding[0],
paddingLeft: padding[1]
;
case 3:
return
paddingTop: padding[0],
paddingRight: padding[1],
paddingBottom: padding[2],
paddingLeft: padding[1]
;
default:
return
paddingTop: padding[0],
paddingRight: padding[1],
paddingBottom: padding[2],
paddingLeft: padding[3]
;
render()
const
flex,
row,
column,
center,
middle,
left,
right,
top,
bottom,
card,
shadow,
color,
space,
padding,
margin,
animated,
wrap,
style,
children,
...props
= this.props;
const blockStyles = [
styles.block,
flex && flex ,
flex === false && flex: 0 , // reset / disable flex
row && styles.row,
column && styles.column,
center && styles.center,
middle && styles.middle,
left && styles.left,
right && styles.right,
top && styles.top,
bottom && styles.bottom,
margin && ...this.handleMargins() ,
padding && ...this.handlePaddings() ,
card && styles.card,
shadow && styles.shadow,
space && justifyContent: `space-$space` ,
wrap && flexWrap: "wrap" ,
color && styles[color], // predefined styles colors for backgroundColor
color && !styles[color] && backgroundColor: color , // custom backgroundColor
style // rewrite predefined styles
];
if (animated)
return (
<Animated.View style=blockStyles ...props>
children
</Animated.View>
);
return (
<View style=blockStyles ...props>
children
</View>
);
export const styles = StyleSheet.create(
block:
flex: 1
,
row:
flexDirection: "row"
,
column:
flexDirection: "column"
,
card:
borderRadius: theme.sizes.radius
,
center:
alignItems: "center"
,
middle:
justifyContent: "center"
,
left:
justifyContent: "flex-start"
,
right:
justifyContent: "flex-end"
,
top:
justifyContent: "flex-start"
,
bottom:
justifyContent: "flex-end"
,
shadow:
shadowColor: theme.colors.black,
shadowOffset: width: 0, height: 2 ,
shadowOpacity: 0.1,
shadowRadius: 13,
elevation: 2
,
accent: backgroundColor: theme.colors.accent ,
primary: backgroundColor: theme.colors.primary ,
secondary: backgroundColor: theme.colors.secondary ,
tertiary: backgroundColor: theme.colors.tertiary ,
black: backgroundColor: theme.colors.black ,
white: backgroundColor: theme.colors.white ,
gray: backgroundColor: theme.colors.gray ,
gray2: backgroundColor: theme.colors.gray2
);
Text.js
import React, Component from "react";
import Text, StyleSheet from "react-native";
import theme from "./constants";
export default class Typography extends Component
render()
const
h1,
h2,
h3,
title,
body,
caption,
small,
size,
transform,
align,
// styling
regular,
bold,
semibold,
medium,
weight,
light,
center,
right,
spacing, // letter-spacing
height, // line-height
// colors
color,
accent,
primary,
secondary,
tertiary,
black,
white,
gray,
gray2,
style,
children,
...props
= this.props;
const textStyles = [
styles.text,
h1 && styles.h1,
h2 && styles.h2,
h3 && styles.h3,
title && styles.title,
body && styles.body,
caption && styles.caption,
small && styles.small,
size && fontSize: size ,
transform && textTransform: transform ,
align && textAlign: align ,
height && lineHeight: height ,
spacing && letterSpacing: spacing ,
weight && fontWeight: weight ,
regular && styles.regular,
bold && styles.bold,
semibold && styles.semibold,
medium && styles.medium,
light && styles.light,
center && styles.center,
right && styles.right,
color && styles[color],
color && !styles[color] && color ,
// color shortcuts
accent && styles.accent,
primary && styles.primary,
secondary && styles.secondary,
tertiary && styles.tertiary,
black && styles.black,
white && styles.white,
gray && styles.gray,
gray2 && styles.gray2,
style // rewrite predefined styles
];
return (
<Text style=textStyles ...props>
children
</Text>
);
const styles = StyleSheet.create(
// default style
text:
fontSize: theme.sizes.font,
color: theme.colors.black
,
// variations
regular:
fontWeight: "normal"
,
bold:
fontWeight: "bold"
,
semibold:
fontWeight: "500"
,
medium:
fontWeight: "500"
,
light:
fontWeight: "200"
,
// position
center: textAlign: "center" ,
right: textAlign: "right" ,
// colors
accent: color: theme.colors.accent ,
primary: color: theme.colors.primary ,
secondary: color: theme.colors.secondary ,
tertiary: color: theme.colors.tertiary ,
black: color: theme.colors.black ,
white: color: theme.colors.white ,
gray: color: theme.colors.gray ,
gray2: color: theme.colors.gray2 ,
// fonts
h1: theme.fonts.h1,
h2: theme.fonts.h2,
h3: theme.fonts.h3,
title: theme.fonts.title,
body: theme.fonts.body,
caption: theme.fonts.caption,
small: theme.fonts.small
);
Button.js
import React, Component from "react";
import StyleSheet, TouchableOpacity from "react-native";
import LinearGradient from "react-native-linear-gradient";
import theme from "./constants";
class Button extends Component
render()
const
style,
opacity,
gradient,
color,
startColor,
endColor,
end,
start,
locations,
shadow,
children,
...props
= this.props;
const buttonStyles = [
styles.button,
shadow && styles.shadow,
color && styles[color], // predefined styles colors for backgroundColor
color && !styles[color] && backgroundColor: color , // custom backgroundColor
style
];
if (gradient)
return (
<TouchableOpacity
style=buttonStyles
activeOpacity=opacity
...props
>
<LinearGradient
start=start
end=end
locations=locations
style=buttonStyles
colors=[startColor, endColor]
>
children
</LinearGradient> */
</TouchableOpacity>
);
return (
<TouchableOpacity
style=buttonStyles
activeOpacity=opacity || 0.8
...props
>
children
</TouchableOpacity>
);
Button.defaultProps =
startColor: theme.colors.primary,
endColor: theme.colors.secondary,
start: x: 0, y: 0 ,
end: x: 1, y: 1 ,
locations: [0.1, 0.9],
opacity: 0.8,
color: theme.colors.white
;
export default Button;
const styles = StyleSheet.create(
button:
borderRadius: theme.sizes.radius,
height: theme.sizes.base * 3,
justifyContent: "center",
marginVertical: theme.sizes.padding / 3
,
shadow:
shadowColor: theme.colors.black,
shadowOffset: width: 0, height: 2 ,
shadowOpacity: 0.1,
shadowRadius: 10
,
accent: backgroundColor: theme.colors.accent ,
primary: backgroundColor: theme.colors.primary ,
secondary: backgroundColor: theme.colors.secondary ,
tertiary: backgroundColor: theme.colors.tertiary ,
black: backgroundColor: theme.colors.black ,
white: backgroundColor: theme.colors.white ,
gray: backgroundColor: theme.colors.gray ,
gray2: backgroundColor: theme.colors.gray2 ,
gray3: backgroundColor: theme.colors.gray3 ,
gray4: backgroundColor: theme.colors.gray4
);
Input.js
import React, Component from "react";
import StyleSheet, View, Animated from "react-native";
import theme from "./constants";
export default class Block extends Component
handleMargins()
const margin = this.props;
if (typeof margin === "number")
return
marginTop: margin,
marginRight: margin,
marginBottom: margin,
marginLeft: margin
;
if (typeof margin === "object")
const marginSize = Object.keys(margin).length;
switch (marginSize)
case 1:
return
marginTop: margin[0],
marginRight: margin[0],
marginBottom: margin[0],
marginLeft: margin[0]
;
case 2:
return
marginTop: margin[0],
marginRight: margin[1],
marginBottom: margin[0],
marginLeft: margin[1]
;
case 3:
return
marginTop: margin[0],
marginRight: margin[1],
marginBottom: margin[2],
marginLeft: margin[1]
;
default:
return
marginTop: margin[0],
marginRight: margin[1],
marginBottom: margin[2],
marginLeft: margin[3]
;
handlePaddings()
const padding = this.props;
if (typeof padding === "number")
return
paddingTop: padding,
paddingRight: padding,
paddingBottom: padding,
paddingLeft: padding
;
if (typeof padding === "object")
const paddingSize = Object.keys(padding).length;
switch (paddingSize)
case 1:
return
paddingTop: padding[0],
paddingRight: padding[0],
paddingBottom: padding[0],
paddingLeft: padding[0]
;
case 2:
return
paddingTop: padding[0],
paddingRight: padding[1],
paddingBottom: padding[0],
paddingLeft: padding[1]
;
case 3:
return
paddingTop: padding[0],
paddingRight: padding[1],
paddingBottom: padding[2],
paddingLeft: padding[1]
;
default:
return
paddingTop: padding[0],
paddingRight: padding[1],
paddingBottom: padding[2],
paddingLeft: padding[3]
;
render()
const
flex,
row,
column,
center,
middle,
left,
right,
top,
bottom,
card,
shadow,
color,
space,
padding,
margin,
animated,
wrap,
style,
children,
...props
= this.props;
const blockStyles = [
styles.block,
flex && flex ,
flex === false && flex: 0 , // reset / disable flex
row && styles.row,
column && styles.column,
center && styles.center,
middle && styles.middle,
left && styles.left,
right && styles.right,
top && styles.top,
bottom && styles.bottom,
margin && ...this.handleMargins() ,
padding && ...this.handlePaddings() ,
card && styles.card,
shadow && styles.shadow,
space && justifyContent: `space-$space` ,
wrap && flexWrap: "wrap" ,
color && styles[color], // predefined styles colors for backgroundColor
color && !styles[color] && backgroundColor: color , // custom backgroundColor
style // rewrite predefined styles
];
if (animated)
return (
<Animated.View style=blockStyles ...props>
children
</Animated.View>
);
return (
<View style=blockStyles ...props>
children
</View>
);
export const styles = StyleSheet.create(
block:
flex: 1
,
row:
flexDirection: "row"
,
column:
flexDirection: "column"
,
card:
borderRadius: theme.sizes.radius
,
center:
alignItems: "center"
,
middle:
justifyContent: "center"
,
left:
justifyContent: "flex-start"
,
right:
justifyContent: "flex-end"
,
top:
justifyContent: "flex-start"
,
bottom:
justifyContent: "flex-end"
,
shadow:
shadowColor: theme.colors.black,
shadowOffset: width: 0, height: 2 ,
shadowOpacity: 0.1,
shadowRadius: 13,
elevation: 2
,
accent: backgroundColor: theme.colors.accent ,
primary: backgroundColor: theme.colors.primary ,
secondary: backgroundColor: theme.colors.secondary ,
tertiary: backgroundColor: theme.colors.tertiary ,
black: backgroundColor: theme.colors.black ,
white: backgroundColor: theme.colors.white ,
gray: backgroundColor: theme.colors.gray ,
gray2: backgroundColor: theme.colors.gray2
);
错误
Error: Unable to resolve module ./components from C:\Users\DELL\wan_way_service_app\App.js:
None of these files exist:
* components(.native|.android.js|.native.js|.js|.android.json|.native.json|.json|.android.ts|.native.ts|.ts|.android.tsx|.native.tsx|.tsx)
* components\index(.native|.android.js|.native.js|.js|.android.json|.native.json|.json|.android.ts|.native.ts|.ts|.android.tsx|.native.tsx|.tsx)
3 |
4 | import theme from './constants';
> 5 | import Button from './components' ;
| ^
6 | import Block from './components' ;
7 | import Text from './components' ;
8 | import Input from './components' ;
【问题讨论】：
【参考方案1】：您是否正确导出了组件？
选项 1 - 如果您要为每个文件导出一个组件，则可以使用“导出默认值”示例：
export default Class ClassName = () =>
return <View />;
并导入使用
import ClassName from './app/components'
选项 2 - 如果有多个组件，则必须以这种方式导出为常量
export Class ClassName = () =>
return <View />;
export Class OtherClassName = () =>
return <View />;
并导入使用
import ClassName, OtherClassName from './app/components'
这取决于创建文件夹结构的方式，默认情况下，对于更简洁的代码，理想情况如下：
myAwesomeProject
src
| components
| | ComponentOne
| | | index.js
| | ComponentTwo
| | | index.js
这样你就可以使用默认导出
【讨论】：
export default class Block extends Component render ()以上是关于为啥在html页面中导入js不能用，在本页又行，，急。。。的主要内容，如果未能解决你的问题，请参考以下文章
为啥我不能在 react native 中导入我的自定义组件
如何在本页提交表单把提交的值显示在本页面上? 请高手把详细的讲解过程给我说一下。谢谢！