1.在utils文件夹下新建一个directives.js文件（命名自己随意）
2.directives.js文件内容如下

const enterNumber = (el, binding) => {
  const wins0 = /[^\d]/g; // 整数判断
  const wins1 = /[^\d^\.]/g; // 小数判断
  let flag = true;
  let points = 0;
  let lengths = 0;
  let remainder = 0;
  let noint = 0;
  const target = el instanceof HTMLInputElement ? el : el.querySelector('input');
  target.addEventListener('compositionstart', e => {
    flag = false;
  });
  target.addEventListener('compositionend', e => {
    flag = true;
  });
  target.addEventListener('input', e => {
    setTimeout(() => {
      if (flag) {
        if (binding.value === 0) {
          if (wins0.test(e.target.value)) {
            e.target.value = e.target.value.replace(/^(\-)*(\d{1})*$/, '$1$2');
            e.target.dispatchEvent(new Event('input')); // 手动更新v-model值
          }
        }
        if (binding.value === 1) {
          e.target.value = e.target.value.replace(/^(\-)*(\d{1})*$/, '$1$2');
          if (wins0.test(e.target.value)) {
            remainder = true;
          }
          if ((e.target.value.split('.')).length - 1 > 1) {
            points = true;
          }
          if (e.target.value.toString().split('.')[1] !== undefined) {
            if (e.target.value.toString().split('.')[1].length > 1) {
              lengths = true;
            }
          }
          if (e.target.value.toString().indexOf('.') !== -1) {
            noint = false;
          } else {
            noint = true;
          }
          if (wins1.test(e.target.value) || lengths || points || remainder) {
            if (!noint) {
              e.target.value = e.target.value.indexOf('.') > 0 ? e.target.value.replace(wins1, '').replace('.', '$#$').replace(/\./g, '').replace('$#$', '.').replace(/^(\-)*(\d+)\.(\d).*$/, '$1$2.$3').substring(0, e.target.value.indexOf('.') + 2) : e.target.value.replace(wins0, '').replace('.', '$#$').replace(/\./g, '').replace('$#$', '.').substring(0, 1);
            } else {
              e.target.value = e.target.value.replace(/^(\-)*(\d{1})*$/, '$1$2');
            }
            e.target.dispatchEvent(new Event('input'));
          }
        }


        if (binding.value === 2) {
          if (wins0.test(e.target.value.toString().replace(/^(\-)*(\d{1})*$/, '$1$2'))) {
            remainder = true;
          }
          if ((e.target.value.split('.')).length - 1 > 1) {
            points = true;
          }
          if (e.target.value.toString().split('.')[1] !== undefined) {
            if (e.target.value.toString().split('.')[1].length > 2) {
              lengths = true;
            }
          }
          if (e.target.value.toString().indexOf('.') !== -1) {
            noint = false;
          } else {
            noint = true;
          }
          if (wins1.test(e.target.value) || lengths || points || remainder) {
            if (!noint) {
              e.target.value = e.target.value.replace(wins1, '').replace('.', '$#$').replace(/\./g, '').replace('$#$', '.').replace(/^(\-)*(\d+)\.(\d\d).*$/, '$1$2.$3').substring(0, e.target.value.indexOf('.') + 3);
            } else {
              e.target.value = e.target.value.replace(/^(\-)*(\d{1})*$/, '$1$2');
            }
            e.target.dispatchEvent(new Event('input'));
          }
        }
      }
    }, 0);
  });
};
export default enterNumber;

3.在main.js中注册全局指令

import enterNumber from '@/utils/directives.js'; // 引入鼠标拖拽滚动图片指令文件
// 注册输入框限制图片指令
Vue.directive('enterNumber', enterNumber);

4.最后在组件中使用

<input v-model="num" type="number" v-enterNumber="1">