B站 React教程笔记day1（4）调色板案例

视频地址

 main.js

import React from "react"
import { render } from "react-dom"
import App from "./App.js"

render(
  <App></App>,
  document.getElementById("app-container")
)

App.js

// 引入 React 和 Component 组件
import React, { Component } from "react";
import Bar from "./components/Bar/Bar.js";
import "./app.less";

class App extends Component {
  constructor() {
    super()

    this.state = {
      r: 128,
      g: 128,
      b: 128
    }

    // 三个 Bar 实例
    this.bars = ['r', 'g', 'b'].map((item, index) => {
      return <Bar key={index} v={this.state[item]} color={item} setColor={(this.setColor).bind(this)}></Bar>
    })
  }

  // 设置函数，可以改变 color 颜色为 value
  setColor(color, value) {
    this.setState({ [color]: value })
  }
  render() {
    return (
      <div>
        <div className="box" style={{ "backgroundColor": `rgb(${this.state.r},${this.state.g},${this.state.b})` }}></div>
        {this.bars}
      </div>
    )
  }
}

//向外暴露
export default App;

app.less

.box {
   200px;
  height: 200px;
  border: 1px solid #333;
}

Bar.js

import React from "react";
import "./css.less";
import {PropTypes} from "prop-types";

class Bar extends React.Component {
  constructor(props) {
    super()

    this.state = {
      v: props.v
    }

    // 绑定this
    this.change = (this.change).bind(this)

    this.setColor = props.setColor
  }

  // 改变颜色
  change(event) {
    this.setState({'v': parseInt(event.target.value)})
    this.setColor(this.props.color, this.state.v)
  }

  render() {
    return (
      <div className="Bar_kaola">
        <div className="bar">
          {this.props.v}
          <input type="range" min="0" max="255" value={this.state.v} onChange={this.change} />
          <input type="number" min="0" max="255" value={this.state.v} onChange={this.change} />
        </div>
      </div>
    )
  }
}

Bar.propTypes = {
    v     : PropTypes.number.isRequired,
    color : PropTypes.string.isRequired,
    setColor : PropTypes.func.isRequired
}

//向外暴露
export default Bar

Bar/css.less:

.Bar_kaola {
  .bar {
    input[type="number"] {
      width: 50px;
      position: relative;
      top: -2px;
    }

    margin-bottom: 10px;
  }
}

package.json:

  "devDependencies": {
    "@babel/core": "^7.4.4",
    "@babel/plugin-transform-runtime": "^7.4.4",
    "@babel/preset-env": "^7.4.4",
    "@babel/preset-react": "^7.0.0",
    "babel-loader": "^8.0.5",
    "css-loader": "^2.1.1",
    "less": "^3.9.0",
    "less-loader": "^5.0.0",
    "prop-types": "^15.7.2",
    "react": "^16.8.6",
    "react-dom": "^16.8.6",
    "style-loader": "^0.23.1",
    "webpack": "^4.30.0",
    "webpack-cli": "^3.3.2"
  },
  "dependencies": {
    "@babel/runtime": "^7.4.4"
  }

webpack.config.js

const path = require('path');

module.exports = {
  entry: "./app/main.js",
  output: {
    path: path.resolve(__dirname, "dist"),
    filename: "all.js"
  },
  module: {
    rules: [
      {
        test: /.js$/,
        exclude: /node_modules/,
        use: {
          loader: 'babel-loader'
        }
      },
      {
        test: /.less$/,
        use: [
          {
            loader: "style-loader" // creates style nodes from JS strings
          },
          {
            loader: "css-loader" // translates CSS into CommonJS
          },
          {
            loader: "less-loader" // compiles Less to CSS
          }
        ]
      }
    ]
  },
  watch: true
}