const toUpper = str => str.toUpperCase();
const exclaim = str => str + '!';
const shout = x => exclaim(toUpper(x));
<p>shout('hello'); // 输出: "HELLO!"</p>

const compose = (...funcs) => {
  return (value) => {
    return funcs.reduceRight((acc, fn) => fn(acc), value);
  };
};

const add1 = x => x + 1;
const multiply2 = x => x * 2;
const subtract3 = x => x - 3;
<p>const pipeline = compose(subtract3, multiply2, add1);
pipeline(5); // 执行顺序：add1(5)=6 → multiply2(6)=12 → subtract3(12)=9，结果为 9</p>

const pipe = (...funcs) => {
  return (value) => {
    return funcs.reduce((acc, fn) => fn(acc), value);
  };
};

const pipeline = pipe(add1, multiply2, subtract3);
pipeline(5); // add1(5)=6 → multiply2(6)=12 → subtract3(12)=9
</font><p>这种写法更符合直觉，尤其在构建数据处理链时很常见。</p><H3>实际应用场景</H3><p>函数组合适合用于：</p><ul><li>字符串处理：如格式化、清洗、校验等步骤串联</li><li>数据转换：API响应数据经过多层处理后再使用</li><li>React 中的高阶组件（HOC）逻辑复用</li><li>中间件机制（如 Redux）中的 action 处理流程</li></ul><p>例如对用户输入进行处理：</p><font color="#666"><pre class="brush:php;toolbar:false;">
const trim = str => str.trim();
const capitalize = str => str.charAt(0).toUpperCase() + str.slice(1);
const validateNonEmpty = str => str.length > 0 ? str : 'Unknown';
<p>const formatName = pipe(trim, capitalize, validateNonEmpty);
formatName('  john  '); // 输出: "John"</p>