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HTML

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HTML preprocessors can make writing HTML more powerful or convenient. For instance, Markdown is designed to be easier to write and read for text documents and you could write a loop in Pug.

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Adding Classes

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About the <head>

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CSS

About CSS Preprocessors

CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.

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CSS Base

About CSS Base

It's a common practice to apply CSS to a page that styles elements such that they are consistent across all browsers. We offer two of the most popular choices: normalize.css and a reset. Or, choose Neither and nothing will be applied.

Vendor Prefixing

About Vendor Prefixing

To get the best cross-browser support, it is a common practice to apply vendor prefixes to CSS properties and values that require them to work. For instance -webkit- or -moz-.

We offer two popular choices: Autoprefixer (which processes your CSS server-side) and -prefix-free (which applies prefixes via a script, client-side).

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JavaScript

About JavaScript Preprocessors

JavaScript preprocessors can help make authoring JavaScript easier and more convenient.

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Babel includes JSX processing.

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HTML 

              
                <div id="root"></div>
!

CSS 

              
                /**
 * Credit
 * counter desgin is from dribbble (https://dribbble.com/shots/5539678-Stepper-VI)
 * chevron icons are from font-awesome (https://fontawesome.com/icons/chevron-down?style=solid)
**/
html,
body {
  margin: 0;
  padding: 0;
  height: 100%;
  width: 100%;
  background-color: #f26072;
  display: flex;
  align-items: center;
  justify-content: center;
}

.container {
  display: flex;
  align-items: center;
  flex-direction: column;
  min-width: 200px;
}

.number {
  font-size: 72px;
  color: #fbf5f5;
  font-family: Verdana;
  line-height: 1.75em;
  text-align: center;
  user-select: none;
}

.chevron {
  background: transparent center center;
  background-repeat: no-repeat;
  cursor: pointer;
  width: 70px;
  height: 70px;
  transition: background-image 0.3s;
}

.chevron-up {
  background-image: url("data:image/svg+xml, %3Csvg aria-hidden='true' focusable='false' role='img' xmlns='http://www.w3.org/2000/svg' viewBox='0 0 448 512'%3E%3Cpath fill='%23f6909c' d='M240.971 130.524l194.343 194.343c9.373 9.373 9.373 24.569 0 33.941l-22.667 22.667c-9.357 9.357-24.522 9.375-33.901.04L224 227.495 69.255 381.516c-9.379 9.335-24.544 9.317-33.901-.04l-22.667-22.667c-9.373-9.373-9.373-24.569 0-33.941L207.03 130.525c9.372-9.373 24.568-9.373 33.941-.001z'%3E%3C/path%3E%3C/svg%3E");
}

.chevron-up:hover {
  background-image: url("data:image/svg+xml, %3Csvg aria-hidden='true' focusable='false' role='img' xmlns='http://www.w3.org/2000/svg' viewBox='0 0 448 512'%3E%3Cpath fill='%23fbf5f5' d='M240.971 130.524l194.343 194.343c9.373 9.373 9.373 24.569 0 33.941l-22.667 22.667c-9.357 9.357-24.522 9.375-33.901.04L224 227.495 69.255 381.516c-9.379 9.335-24.544 9.317-33.901-.04l-22.667-22.667c-9.373-9.373-9.373-24.569 0-33.941L207.03 130.525c9.372-9.373 24.568-9.373 33.941-.001z'%3E%3C/path%3E%3C/svg%3E");
}

.chevron-down {
  background-image: url("data:image/svg+xml,%3Csvg aria-hidden='true' focusable='false' xmlns='http://www.w3.org/2000/svg' viewBox='0 0 448 512'%3E%3Cpath fill='%23f6909c' d='M207.029 381.476L12.686 187.132c-9.373-9.373-9.373-24.569 0-33.941l22.667-22.667c9.357-9.357 24.522-9.375 33.901-.04L224 284.505l154.745-154.021c9.379-9.335 24.544-9.317 33.901.04l22.667 22.667c9.373 9.373 9.373 24.569 0 33.941L240.971 381.476c-9.373 9.372-24.569 9.372-33.942 0z'%3E%3C/path%3E%3C/svg%3E");
}

.chevron-down:hover {
  background-image: url("data:image/svg+xml,%3Csvg aria-hidden='true' focusable='false' xmlns='http://www.w3.org/2000/svg' viewBox='0 0 448 512'%3E%3Cpath fill='%23fbf5f5' d='M207.029 381.476L12.686 187.132c-9.373-9.373-9.373-24.569 0-33.941l22.667-22.667c9.357-9.357 24.522-9.375 33.901-.04L224 284.505l154.745-154.021c9.379-9.335 24.544-9.317 33.901.04l22.667 22.667c9.373 9.373 9.373 24.569 0 33.941L240.971 381.476c-9.373 9.372-24.569 9.372-33.942 0z'%3E%3C/path%3E%3C/svg%3E");
}
!

JS 

              
                const { useState } = React;

const counters = Array.from({ length: 14 }, (_, index) => index);

// STEP 2：透過 props 取得外層傳入的資料
const Counter = props => {
  // STEP 3: 使用解構賦值把需要的資料從 props 中取出
  const { startingValue, minNumber, maxNumber } = props;
  
  // STEP 4: 把 startingValue 當作 count 的預設值放入 useState 的參數中
  const [count, setCount] = useState(startingValue);

  const handleIncrement = () => setCount(count + 1);
  const handleDecrement = () => setCount(count - 1);

  return (
    <div className="container">
      <div
        className="chevron chevron-up"
        onClick={handleIncrement}
        // STEP 5: 把 maxNumber 帶入判斷式
        style={{
          visibility: count >= maxNumber && "hidden"
        }}
      />

      <div className="number">{count}</div>

      <div
        className="chevron chevron-down"
        onClick={handleDecrement}
        // STEP 6: 把 minNumber 帶入判斷式
        style={{
          visibility: count <= minNumber && "hidden"
        }}
      />
    </div>
  );
};

ReactDOM.render(
  <div
    style={{
      display: "flex",
      flexWrap: "wrap"
    }}
  >
    {/* counters.map(item => <Counter />) */}
    {/* STEP 1：將需要的資料透過 props 傳入 */}
    <Counter startingValue={5} minNumber={1} maxNumber={10} />
    <Counter startingValue={15} minNumber={11} maxNumber={20} />
    <Counter startingValue={25} minNumber={21} maxNumber={30} />
    <Counter startingValue={35} minNumber={31} maxNumber={40} />
    <Counter startingValue={45} minNumber={41} maxNumber={50} />
  </div>,
  document.getElementById("root")
);
!
999px

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